RED BLOOD CELL DISORDER:

ANEMIA
Subibe, Denarah A.
 TABLE OF CONTENTS

01 Iron deficiency anemia 04 Alpha thalassemia

Other causes of
02 hypoproliferative 05 Megaloblastic anemia
anemias

03 Beta thalassemia 06 Hemolytic anemia

 TABLE OF CONTENTS

Anemia due to acute

07 blood loss

08 Aplastic anemia

09 Myelodysplasia
 Iron deficiency anemia

● Major role of iron is to carry O2 as part of

hemoglobin
● Iron is a critical element in in iron-containing
enzymes, including the cytochrome system in
mitochondria
● Without iron, in erythroid cells, hemoglobin
synthesis is impaired, resulting in anemia and
reduced O2 delivery in tissues.
 Nutritional iron balance

● Iron Balance: Tightly regulated with no specific excretion pathway; lost mainly through blood loss and
skin/epithelial shedding.
● Absorption Sources:
○ Heme iron (from animal sources) is better absorbed than non-heme iron (from plants).
○ Absorption efficiency: ~6% in men, ~12% in women; higher with meat diets, lower in vegetarian diets.
○ Inhibitors like phytates and phosphates can reduce absorption by ~50%.
● Higher Requirements: Women, infants, children, adolescents, and pregnant women have increased iron
needs.
● Absorption Location: Primarily in the duodenum and proximal small intestine, facilitated by stomach acidity.
● Key Proteins:
○ DMT-1: Transports iron into gut cells.
○ Ferroportin: Exports iron into the bloodstream.
○ Hepcidin: Regulates iron release by inhibiting ferroportin.
○ Hephaestin: Oxidizes iron for transferrin binding.
● ERFE: Suppresses hepcidin production; prolonged suppression can lead to iron overload and tissue damage.
 Stages of iron deficiency, their mechanism,
causes, laboratory indicators and differences
 Clinical manifestations

● Iron deficiency is more likely during pregnancy, adolescence, rapid growth, or with a history of
blood loss.
● In adult males and postmenopausal females, it often indicates gastrointestinal blood loss.
● Advanced signs include cheilosis (mouth fissures) and koilonychia (spoon-shaped nails).
● Diagnosis is based on laboratory results.
 Laboratory iron studies

● Serum Iron: Measures circulating iron bound to transferrin; normal range is 50–150 µg/dL.
● Total Iron-Binding Capacity (TIBC): Indicates available transferrin for iron binding; normal range is 300–360
µg/dL.
● Transferrin Saturation: Calculated as (serum iron×100)÷TIBC(\text{serum iron} \times 100) \div
\text{TIBC}(serum iron×100)÷TIBC; normal saturation is 25–50%. Levels <20% indicate iron deficiency; levels
>50% suggest iron overload.
● Serum Ferritin: Reflects total body iron stores; normal values are 100 µg/L for males and 30 µg/L for females.
A level <15 µg/L indicates depleted iron stores.
 Differential diagnosis

Thalassemias:

● Inherited defects in globin chain synthesis.

● Differentiated from iron deficiency by normal/elevated serum iron and transferrin saturation; RDW is usually
normal.

Anemia of Inflammation (AI):

● Often normocytic/normochromic but can present as hypochromic microcytic anemia.

● Ferritin is normal/increased; transferrin saturation and TIBC are usually low; differentiation relies on iron
studies.

Myelodysplastic Syndromes:

● Rarely cause microcytic hypochromic anemia.

● Result from impaired iron incorporation into heme despite adequate iron stores.
Approach to treatment of iron deficiency anemia
Major Therapeutic Approaches:

1. Red Cell Transfusion:

○ Indicated for symptomatic anemia or severe blood loss; provides immediate correction and iron.
2. Oral Iron Therapy:
○ For asymptomatic patients with good gastrointestinal function.
○ Encourage dietary iron (oysters, beef liver, legumes).
○ Typical dose: 200 mg elemental iron daily; side effects include gastrointestinal distress (15–20%).
○ Therapy response expected in 4–7 days; consider parenteral iron if absorption issues arise.
3. Parenteral Iron Therapy:
○ For patients intolerant to oral iron or with urgent needs.
○ New formulations (e.g., ferumoxytol) have fewer side effects.
○ Dosage based on body weight and hemoglobin deficit; low risk of anaphylaxis, but caution is advised for those
with allergies.
 Other
Hypoproliferative
Anemias
 Anemia of acute and chronic
inflammation
Anemia of Acute and Chronic Inflammation (AI)
○ Common in conditions involving inflammation, infection, tissue injury, or cancer. AI is characterized
by inadequate iron delivery to the marrow despite normal or increased iron stores.
○ Low serum iron, increased red cell protoporphyrin, hypoproliferative marrow.
○ Transferrin saturation: 15–20%.
○ Serum ferritin: Normal or elevated, often threefold higher in inflammation, helping distinguish AI
from iron-deficiency anemia.
Cytokine Effects:
○ Inflammatory cytokines (IL-1, TNF, IFN) suppress erythropoiesis and reduce responsiveness to
erythropoietin (EPO).
○ Hepcidin, increased by IL-6 during inflammation, inhibits iron absorption and release from storage.
Erythropoietic Impact:
● Chronic inflammation leads to hypoproliferative anemia, with decreased red cell survival. Anemia is
typically normocytic and normochromic but can be microcytic and hypochromic in chronic
conditions like rheumatoid arthritis and tuberculosis.
Diagnosis:
○ AI is distinguished by elevated serum ferritin and altered iron metabolism.
○ Soluble transferrin receptor protein may be measured to rule out concurrent iron deficiency in
cases of chronic blood loss
 Anemia of renal disease
Anemia of Chronic Kidney Disease (CKD)
Progressive CKD is commonly associated with moderate to severe hypoproliferative anemia, correlating with the
stage of CKD.
Causes:
- Primary cause: Reduced erythropoietin (EPO) production by diseased kidneys.
- Additional factor: Decreased red cell survival.

Red Cell Characteristics:

- Normocytic, normochromic red cells.
- Decreased reticulocyte count.

- Iron Status:
- Typically normal serum iron, TIBC, and ferritin in CKD patients.
- Patients on chronic hemodialysis may develop iron deficiency due to blood loss during dialysis, necessitating
iron replenishment to support EPO therapy.
 Anemia of hypometabolic state
Anemia in Hypometabolic States

Overview: Hypometabolic states such as starvation and endocrine disorders can lead to mild to moderate
hypoproliferative anemia.

Endocrine Deficiency States:

EPO production: Triggered by lower oxygen demand in conditions like hypothyroidism or starvation.

Effects of hormones:
Testosterone and anabolic steroids: Stimulate erythropoiesis.
Castration and estrogen administration: Reduce erythropoiesis.

Associated disorders:
Hypothyroidism: Mild anemia, often reversed with hormone replacement.
Addison's disease: Anemia severity depends on androgen and thyroid dysfunction. Hemoglobin levels may fall
rapidly after cortisol and fluid replacement.
Hyperparathyroidism: Anemia may arise from reduced EPO production due to renal effects of hypercalcemia.
 Anemia of hypometabolic state
Protein Starvation:
Mechanism: Protein deficiency decreases EPO release in proportion to reduced metabolic rate.
Severity: More severe in marasmus (combined protein and calorie deficiency).
Masked anemia: Volume depletion may hide the extent of anemia, which becomes evident after refeeding.
Complications: Iron, folate, and B12 deficiencies may complicate the clinical picture.

Anemia in Liver Disease:

Causes: Common in chronic liver disease, with features like spur cells and stomatocytes due to excess
cholesterol in red cell membranes.
Red cell survival: Shortened, with inadequate EPO production to compensate.
Alcoholic liver disease: Nutritional deficiencies, especially folate and iron, are frequent and may alter red cell
indices.
 Treatment in hypoproliferative
1. Transfusions:
anemias
- When: Used if hemoglobin drops below 7–8 g/dL in healthy patients or <11 g/dL in those with
cardiovascular/pulmonary issues.
- 1 unit of blood increases hemoglobin by 1 g/dL.
- Risks: Infections, iron overload, and higher morbidity in intensive care settings. A conservative transfusion
approach is preferred.

2. Erythropoietin (EPO) Therapy:

- Uses: Effective in anemia due to low EPO, like in chronic kidney disease (CKD) or inflammation.
- Dosing: 50–150 U/kg three times per week IV for CKD. Target hemoglobin: 10–12 g/dL. Higher doses (up to 300
U/kg) needed for chemotherapy-induced anemia.
- Iron supplementation is crucial for success.
- Risks: Thromboembolic events and tumor progression in cancer patients, requiring careful use.

3. Longer-Acting EPO:
- Darbepoetin Alfa: Requires less frequent dosing (weekly or biweekly) due to its longer half-life.

4. EPO Mimetics:
- Roxadustat: Oral drug used in chronic renal disease to increase hemoglobin, dosed at 50 mg three times
weekly.
Thalassemia
syndromes
 Beta thalassemia
● Single nucleotide changes are the most common thalassemia mutations; gene deletions also occur.
● Mutation types include those affecting gene transcription, mRNA processing, splicing, RNA polyadenylation,
and translation.
● In β thalassemia, excess α-globin chains accumulate, leading to membrane damage and ineffective
erythropoiesis (anemia).
● Severe untreated β thalassemia causes anemia, organ damage, and complications like hepatosplenomegaly
and iron overload.
● Treatment with transfusions, iron chelation, and stem cell transplantation can prevent or cure severe
cases.
FORMS OF BETA THALASSEMIA, AND THEIR CHARACTERISTICS
Diagnosis of Thalassemia:

● Heterozygous β Thalassemia (Trait/Minor):

○ Mild/no anemia, microcytic/hypochromic erythrocytes.
○ Normal or slightly elevated reticulocyte count.
○ Diagnostic Test: Elevated HbA2 and possibly HbF levels via HPLC (after excluding iron deficiency).
○ Other Characteristics: Sometimes spleen enlargement.
○ Importance of Mutation Identification: Helps in genetic counseling and preventing severe
transfusion-dependent thalassemia in offspring.
● Severe β Thalassemia:
○ Features hemolytic anemia with microcytosis, hypochromia, reticulocytosis, anisocytosis, poikilocytosis, and
nucleated red blood cells.
Treatment Approaches:

1. Transfusion and Iron Chelation:

○ Regular transfusions (every 2-4 weeks) maintain hemoglobin at 9–10.5 g/dL.
○ Chelation Therapy: Deferasirox, deferiprone (oral), and deferoxamine (intravenous) prevent iron
overload, extending life expectancy to over 50 years.
○ Lifelong treatment to avoid complications such as cardiomyopathy, osteoporosis, and liver disease.
2. Hematopoietic Stem Cell Transplantation:
○ Indicated for: Patients with matched sibling donors.
○ Curative in >80% of cases; best results in younger patients with effective chelation and fewer
transfusions.
○ Risks: Graft failure, rejection, graft-versus-host disease, with 5–20% mortality depending on risk
factors.
3. Improving Ineffective Erythropoiesis:
○ Luspatercept: A newly approved drug that reduces transfusion requirements by enhancing late-stage
erythropoiesis.
4. Gene Therapy:
○ Lentiviral Gene Therapy: Approved in Europe for transfusion-dependent patients without a matched
donor.
■ Reduced/eliminated transfusions with stable hemoglobin levels (8.2–13.7 g/dL).
■ Limitations: Dependent on the mutation, ineffective erythropoiesis persists.
○ CRISPR/Cas Gene Editing: Promising early results in reducing transfusion needs and normalizing
hemoglobin levels.
 Alpha thalassemia
Fetal stage: Reduced or absent α-globin synthesis leads to the formation of γ₄ tetramers (Hb Bart’s) from unpaired
γ-globin chains.
Adult stage: Without sufficient α-globin, β₄ tetramers (HbH) form from unpaired β-globin chains.
Hb Bart’s and HbH: Both have high oxygen affinity, making them ineffective at oxygen delivery to tissues, and HbH is
unstable, leading to oxidative damage.
Severe anemia:

● Hb Bart’s hydrops fetalis: Caused by lack of functional hemoglobin and ineffective erythropoiesis.
● HbH disease: Unstable HbH causes membrane damage, extravascular hemolysis, and ineffective erythropoiesis.
Fetal stage: Reduced or absent α-globin synthesis leads to the formation of γ₄ tetramers (Hb Bart’s) from unpaired
γ-globin chains.
Adult stage: Without sufficient α-globin, β₄ tetramers (HbH) form from unpaired β-globin chains.
Hb Bart’s and HbH: Both have high oxygen affinity, making them ineffective at oxygen delivery to tissues, and HbH is
unstable, leading to oxidative damage.
Severe anemia:

● Hb Bart’s hydrops fetalis: Caused by lack of functional hemoglobin and ineffective erythropoiesis.
● HbH disease: Unstable HbH causes membrane damage, extravascular hemolysis, and ineffective erythropoiesis.
 Diagnosis of alpha thalassemia

α-Thalassemia Trait: Characterized by microcytosis, hypochromia, and near-normal hemoglobin levels. Iron deficiency is
excluded, and increased HbA₂ (which indicates β-thalassemia) is absent.

HbH Disease: Typically caused by compound heterozygosity (one chromosome with both α-globin genes deleted, and
another with one α-globin gene deleted).

● At birth: Hemoglobin analysis via HPLC shows 20–30% Hb Bart’s.

● In adults: 40% HbH can be present, with some residual Hb Bart’s.
● Reticulocytosis: Varies in severity, depending on the extent of α-globin deletion.
● HbH inclusions can be identified by staining red blood cells with brilliant cresyl blue.

Management of α-Thalassemia:

1. Iron Management:
○ Avoid iron supplementation in individuals with α-thalassemia trait who are not iron-deficient.
○ Regularly monitor iron stores (serum ferritin or MRI) in patients, especially those with HbH disease.
2. Transfusions:
○ Typically, transfusions are not required for HbH disease.
○ Transfusions may be necessary in specific cases, such as during pregnancy or acute anemic episodes when
anemia worsens.
3. Hb Bart’s Hydrops Fetalis:
○ Best managed through prevention by screening and antenatal diagnosis.
○ Intrauterine therapy and perinatal intensive care may improve survival, but prevention is preferred due to
associated complications in survivors.
Megaloblastic
anemia
 Megaloblastic anemia
Megaloblastic Anemias:

● A group of disorders characterized by abnormal red cell development in the bone marrow.
● Typically caused by ineffective erythropoiesis due to deficiencies in cobalamin (vitamin B12) or folate.
● May also result from genetic or acquired defects in DNA synthesis unrelated to cobalamin or folate.
Nutrient Cobalamin Folate

Daily Adult 1–3 µg 100 µg

Requirement

Body Stores 2–3 mg (sufficient for 3–4 years) 10 mg (sufficient for 3–4 months)

Dietary Sources Meat, Fish, Dairy products Liver, Yeast, Spinach, Greens, Nuts

Cooking Stability Heat stable Easily destroyed by heat, especially in

water

Absorption Mechanism - Passive absorption: Occurs in buccal, Absorbed from the upper small intestine
duodenal, ileal mucosa; inefficient (<1% - Polyglutamates converted to
absorption). monoglutamates before absorption.
- Active absorption: Occurs in the ileum via - Active transport mediated by
intrinsic factor (IF) produced by gastric proton-coupled folate transporter (PCFT)
parietal cells, and binds to specific receptors at the brush border of the duodenum and
(cubilin) in the ileum. jejunum.
- Cobalamin is released from dietary proteins, - Folates are absorbed primarily as
binds to haptocorrins (HCs) in the stomach, 5-methyl-tetrahydrofolate (5-MTHF), the
and is later transferred to intrinsic factor (IF) main circulating form of folate.
in the intestine. - 50% of dietary folate is absorbed; the
- The IF-cobalamin complex is absorbed in efficiency depends on the form
the ileum and transported to plasma via (monoglutamate vs. polyglutamate).
transcobalamin II (TC II).
Nutrient Cobalamin Folate

Transport in Blood - Transported by transcobalamin II (TC II). - Mostly unbound 5-MTHF in plasma;
- Cobalamin bound to transcobalamin is one-third is loosely bound to albumin.
delivered to tissues via receptor-mediated - Transport into cells is mediated by
endocytosis. reduced folate transporter (RFC) and
- Excess cobalamin is reabsorbed through folate receptors (FR2, FR3).
enterohepatic circulation (bile) daily. - Folate also undergoes enterohepatic
circulation, where 60-90 µg of folate is
reabsorbed from bile.
Function Cobalamin Folate

Main Role Acts as coenzymes in the transfer of Involved in the conversion of

single-carbon units. homocysteine to methionine.

Purine and Pyrimidine Folates are essential for purine synthesis Required for methionine synthesis
Synthesis and pyrimidine synthesis (for DNA and RNA (regeneration of THF).
replication).

Key Reaction 5,10-methylene-THF is essential in the Works as a coenzyme in methionine

conversion of deoxyuridine monophosphate synthase reaction alongside folate.
(dUMP) to deoxythymidine monophosphate
(dTMP), which is necessary for DNA
synthesis.

Enzyme Inhibition The drugs methotrexate, pyrimethamine, Deficiency leads to failure of converting
and trimethoprim inhibit dihydrofolate dUMP to dTMP due to lack of
reductase (DHF reductase), which is 5,10-methylene-THF.
essential for recycling THF.

Role in Megaloblastic Folate deficiency leads to impaired DNA Cobalamin deficiency impairs methionine
Anemia synthesis, causing ineffective erythropoiesis synthase activity and the conversion of
and resulting in megaloblastic changes in the dUMP to dTMP, which also causes
bone marrow. megaloblastic anemia.
 Megaloblastic anemia
Clinical Manifestations:

● Fatigue, weakness, pallor, and shortness of breath.

● Gastrointestinal issues: anorexia, weight loss, glossitis, and bowel changes (diarrhea/constipation).
● Possible jaundice, skin hyperpigmentation, and thrombocytopenia, increasing infection risk.

Neurologic Manifestations (more common in B12 deficiency):

● Bilateral peripheral neuropathy and spinal cord degeneration (demyelination).

● Symptoms may include paresthesias, muscle weakness, difficulty walking, and loss of proprioception and vibration
sensation.
● Cognitive symptoms: dementia, depression, psychosis, and visual impairment.

Cognitive Impairment:

● Elevated homocysteine levels linked to cognitive decline and dementia risk.

● Mixed evidence regarding the effectiveness of B-vitamin supplementation in improving cognitive function.
General Tissue Effects of Cobalamin and Folate Deficiencies

● Epithelial Surfaces:
○ Mouth (glossitis), stomach, small intestine, and various tracts (respiratory, urinary, female genital).
○ Cervical smear abnormalities.
● Pregnancy Complications:
○ Infertility in both genders.
○ Maternal folate deficiency is linked to prematurity, recurrent fetal loss, and neural tube defects (NTDs).
Folic acid supplements during conception reduce NTD incidence by about 70%.
● Neural Tube Defects (NTDs):
○ Folic acid supplementation (0.4 mg daily) is effective in reducing NTD risk.
○ The MTHFR C677T polymorphism is associated with lower folate levels and increased risk for NTDs.
● Cardiovascular Disease:
○ Severe homocystinuria due to cobalamin/folate deficiencies can lead to early vascular diseases.
○ Elevated homocysteine levels and lower folate are linked to increased risks of cardiovascular issues,
though trials have shown mixed results regarding supplementation benefits.
● Malignancy:
○ Folic acid during pregnancy may reduce the incidence of acute lymphoblastic leukemia (ALL) in children.
○ Mixed associations exist between folate status/polymorphisms and various cancers (e.g., colorectal
cancer, breast cancer, gastric cancer).
○ Prophylactic folic acid may protect against certain tumors but could potentially "feed" existing tumors,
warranting caution in patients with malignancies.
HEMATOLOGIC FINDINGS

Finding Description

Peripheral Blood Oval macrocytes, anisocytosis, poikilocytosis

MCV Typically >100 fL

Neutrophils Hypersegmented (>5 lobes)

Leukopenia Possible, usually >1.5 × 109/L

Platelets Moderately reduced, rarely <40 × 109L

Bone Marrow Hypercellular, primitive cells with apoptosis of mature forms

Chromosomal Changes Random breaks, exaggeration of constrictions

Ineffective Unconjugated bilirubin accumulation, signs of hemolysis

Hematopoiesis
CAUSES OF COBALAMIN DEFICIENCY
CAUSES OF FOLATE DEFICIENCY
DIAGNOSIS

Deficiency Tests and Findings

Cobalamin Deficiency Serum Cobalamin: <74 pmol/L indicates deficiency. Borderline: 74–148 pmol/L.
Serum MMA & Homocysteine: Elevated in deficiency; aids early diagnosis.
Potential Causes: Vegan diet, pernicious anemia, absorption issues, atrophic
gastritis.
Tests for PA: Elevated serum gastrin, low serum pepsinogen I, tests for intrinsic
factor antibodies.

Folate Deficiency Serum Folate: Low levels (<11 nmol/L) indicate deficiency.
Red Cell Folate: Indicates body stores; low in folate and severe cobalamin
deficiency.
Tests for Cause: Dietary history, transglutaminase antibodies for celiac disease.
TREATMENT

Cobalamin Deficiency

● Lifelong Treatment: Regular injections (hydroxocobalamin in the UK, cyanocobalamin in the US).
● Dosage:
○ Replenishment: Six 1000 µg IM injections over 3-7 days.
○ Maintenance: Hydroxocobalamin: 1000 µg IM every 3 months; Cyanocobalamin: 1000 µg IM monthly.
● Oral Therapy: High doses (1000-2000 µg) of cyanocobalamin can be used if absorption is impaired.
● Special Cases: Provide therapy to patients post-gastrectomy or with intestinal disorders.

Folate Deficiency

● Oral Supplementation: 5-15 mg of folic acid daily.

● Duration: Continue for about 4 months or longer if the underlying condition persists.
● Caution: Exclude cobalamin deficiency before starting folate treatment to avoid neuropathy.
● Long-term Use: Needed for chronic conditions (e.g., chronic dialysis).

Prophylactic Use

● Pregnancy: 400 µg daily folic acid supplement to prevent NTDs; higher doses for high-risk pregnancies.
● Infants: Routine folic acid for premature infants.
Hemolytic
anemia
Types of hemolytic anemias: HAs can be inherited or acquired, acute or chronic, and range in severity. Hemolysis can
happen within the bloodstream (intravascular) or outside of it (extravascular).
Laboratory features of hemolytic anemias
Hemolysis:

● Extravascular hemolysis: Increased unconjugated bilirubin, AST, and urobilinogen in urine and stool.
● Intravascular hemolysis: Signs include hemoglobinuria, elevated LDH, reduced haptoglobin, and possibly
normal or mildly increased bilirubin.

Bone Marrow Response:

● Elevated reticulocyte count and mean corpuscular volume (MCV), seen as macrocytes on blood smears with
possible polychromasia and nucleated red cells.
● A bone marrow aspirate may show erythroid hyperplasia, though it's usually unnecessary.
● Red Cell Differentiation:
○ RBCs lose their nucleus, organelles, and biosynthetic functions while accumulating hemoglobin.
○ Mature RBCs rely on anaerobic glycolysis for ATP production due to the loss of mitochondria.
○ Aged RBCs expose proteins like band 3, leading to antibody recognition and phagocytosis by
macrophages.
● RBC Aging and Turnover:
○ Normal RBC lifespan is ~120 days; in hemolytic anemia (HA), RBCs are destroyed prematurely.
○ Accelerated phagocytosis of senescent RBCs increases turnover, measurable via red cell survival studies
(e.g., 51Cr or 15N isotopes).
● Consequences of Increased RBC Destruction:
○ Acute hemolysis necessitates more erythropoietic factors (e.g., folic acid).
○ Chronic hemolysis results in elevated bilirubin, gallstone formation, splenomegaly, and hypersplenism,
impacting neutrophils and platelets.
● Iron Metabolism:
○ Chronic intravascular hemolysis leads to iron loss (hemoglobinuria).
○ Chronic extravascular hemolysis may cause iron overload, particularly with blood transfusions, potentially
resulting in hemochromatosis affecting the liver and heart.
Differences between compensated hemolysis versus hemolytic anemia

Compensated Hemolysis:

● Involves the same processes as hemolytic anemia but does not lead to anemia.
● Patients may not exhibit anemia despite hemolysis; however, they could develop anemia under conditions like
pregnancy, folate deficiency, or renal failure (which lowers EPO production).

Hemolytic Anemia (HA):

● Chronic HAs can worsen with intercurrent conditions (e.g., acute infections), causing significant reductions in red
cell production and hemoglobin levels.
● Example: Parvovirus B19 infection can induce an aplastic crisis, leading to a sudden and severe drop in
hemoglobin due to erythropoiesis suppression.
Inherited HA
 1. Hereditary
spherocytosis
Genetics and Inheritance:
● HS is genetically heterogeneous, arising from various mutations in different genes related to the red cell
membrane.
● It is typically inherited in an autosomal dominant manner, though severe cases can result from autosomal
recessive inheritance.

Clinical Presentation:
● Severity varies widely:
○ Severe cases may present in infancy with severe anemia.
○ Mild cases may go unnoticed until young adulthood or later.
● Common features include jaundice, splenomegaly, and often gallstones. The detection of gallstones in young
individuals may prompt a diagnostic investigation.

Diagnosis:
● Diagnosis is typically based on clinical features, family history, and blood tests showing normocytic anemia with
increased mean corpuscular hemoglobin concentration (MCHC), increased red cell distribution width
(RDW), and characteristic spherocytes on blood smear.
● The spleen plays a central role in HS by destroying the less deformable RBCs and promoting further cell damage
during circulation.
● Laboratory tests include the osmotic fragility test, acid glycerol lysis test, eosin-5’-maleimide
(EMA)–binding test, and SDS-gel electrophoresis. In some cases, molecular studies may be needed to confirm
gene mutations.
Treatment:

● There is no cure for the underlying

membrane-cytoskeleton defect in HS.
● Splenectomy is often recommended:
○ Severe cases: splenectomy at age 4-6 years.
○ Moderate cases: splenectomy delayed until
puberty.
○ Mild cases: splenectomy avoided.
○ Partial splenectomy may be an option in
specific cases.
● Before splenectomy, vaccination against encapsulated
bacteria like Neisseria meningitidis and
Streptococcus pneumoniae is essential, and
post-splenectomy penicillin prophylaxis is sometimes
considered.
● Cholecystectomy (gallbladder removal) should only
be done if clinically indicated, usually laparoscopically.
2. Hereditary
elliptocytosis
General Features: Genetic and clinical variability, affecting 1:2000–4000 people. Named after the elliptical shape of red
cells.

Mechanism: Defects in red cell cytoskeleton proteins reduce membrane stability, leading to varying degrees of hemolysis.

Classification: Ranges from mild (asymptomatic) to severe (Hereditary Pyropoikilocytosis, HPP), with red cell
fragmentation and anemia.

Examples:

● Southeast Asia Ovalocytosis (SAO): Common in Southeast Asia, protective against malaria.
● HPP: Severe form with splenomegaly and poikilocytosis.

Clinical Presentation: Mild cases are often asymptomatic; severe cases present with anemia, splenomegaly, and
abnormal blood cells.

Diagnosis: Blood smear showing elliptocytes; genetic testing confirms specific mutations.

Treatment:

● Mild cases may not need treatment.

● Severe cases benefit from splenectomy, along with pre-splenectomy vaccinations.
 3. G6PD
deficiency
General Features:

● X-linked genetic disorder, affecting primarily males (hemizygous).

● Females (heterozygous) show variable clinical expression due to X-chromosome inactivation.
● Global prevalence is high in regions like Africa, Southern Europe, Southeast Asia, and the Middle East, linked to malaria
resistance.

Mechanism:

● Caused by mutations in the G6PD gene, leading to decreased stability or function of the G6PD enzyme.
● This results in increased susceptibility of red blood cells to oxidative damage, especially under stress (infection, drugs, fava
beans).

Classification:

● Variants are classified by severity: mild forms (asymptomatic or mild symptoms) vs. severe forms (chronic nonspherocytic
hemolytic anemia, CNSHA).
● Different geographic regions show different G6PD variants, e.g., G6PD Mediterranean, G6PD A– (Africa), G6PD Canton
(China).

Clinical Presentation:

● Most individuals remain asymptomatic, but risk neonatal jaundice (NNJ) or acute hemolytic anemia (AHA) upon exposure to
oxidative stressors.
● Triggers of AHA: Fava beans, infections, certain drugs (e.g., primaquine, rasburicase).
● AHA presents with jaundice, dark urine, anemia, and sometimes renal failure.
● Chronic nonspherocytic hemolytic anemia (CNSHA): Rare, with variable severity, often with a history of NNJ and
gallstones; can cause oxidative stress.
Diagnosis:

● Screening tests for G6PD activity, with confirmation by quantitative tests in acute hemolysis.
● DNA testing for definitive diagnosis, especially in females.

Treatment:

● Preventative: Avoid known oxidative triggers (fava beans, specific drugs).

● AHA: No specific treatment unless severe, in which case transfusions may be required.
● CNSHA: Managed with folic acid, transfusions if needed, and avoidance of triggers.
● Splenectomy: Occasionally beneficial in severe CNSHA, although selective red cell destruction in the spleen is not
prominent in G6PD deficiency.
Acquired HA
1. Autoimmune
HA
Clinical Features:

● Symptoms: Abrupt onset of severe anemia (hemoglobin may drop to 4 g/dL), jaundice, and possible splenomegaly.
● Lab Findings: Elevated reticulocyte count (unless erythroid precursors are also affected) and elevated LDH.

Diagnosis:

● Direct Antiglobulin Test (Coombs Test): Key diagnostic tool. A positive test indicates AIHA.
● Coombs-negative AIHA: May still be severe due to high-affinity antibodies.

Mechanism:

● IgG antibodies target red blood cells, leading to their destruction primarily in the spleen via macrophages.

Associations:

● Can be idiopathic or secondary to conditions like systemic lupus erythematosus (SLE), lymphoproliferative disorders, chronic
lymphocytic leukemia (CLL), and recent immune checkpoint inhibitor therapy.
Treatment

Acute Management:

● Severe cases may require red cell transfusions, even if blood is incompatible.

Initial Therapy:

● Start prednisone (1 mg/kg/day). Rituximab (100 mg/week for 4 weeks) is also used as a first-line treatment to reduce relapse
rates.

Second-line Options:

● Splenectomy: Reduces hemolysis and treatment needs, but carries infection risk.
● Other Agents: Azathioprine, cyclophosphamide, cyclosporine, and intravenous immunoglobulin.

Refractory Cases:

● High-dose cyclophosphamide or anti-CD52 therapy (alemtuzumab) may be necessary.

Supportive Care:

● Erythropoietin may help in cases with reticulocytopenia to reduce transfusion needs.

2. Paroxysmal
Cold
Hemoglobinuri
a
Key Features:

● Characterized by the Donath-Landsteiner antibody, which has anti-P specificity.

● This antibody binds to red blood cells at low temperatures (optimal at 4°C) and causes lysis when warmed to 37°C in the
presence of complement, leading to intravascular hemolysis and hemoglobinuria.

Diagnosis: The diagnosis of PCH requires differentiation from other causes of hemoglobinuria. The presence of the
Donath-Landsteiner antibody is definitive for PCH.

Treatment:

● Supportive Care: May include blood transfusions to manage anemia.

● Prognosis: Recovery is generally expected following treatment.
 3. Cold
Agglutinin
Disease
 ● Temperature Sensitivity: Antibodies react poorly at 37°C but strongly at lower temperatures, causing hemolysis when
exposed to cold.
● Antibody Type: Typically IgM with anti-I specificity produced by autoreactive B lymphocytes.

Mechanism:

● Hemolysis: IgM activates the complement system, leading to both intravascular and extravascular hemolysis.

Management:

● Mild Cases: Avoid cold exposure.

● Severe Cases:
○ Rituximab: First-line treatment, effective in up to 60% of patients.
○ Other Treatments: Plasma exchange, B-cell inhibitors (venetoclax, ibrutinib), and complement inhibitors
(eculizumab, sutimlimab) for relapses.

Supportive Care: Blood transfusions may be needed, but it’s important to keep the patient warm during the procedure.

●
 Paroxysmal
Nocturnal
Hemoglobinuri
a
Triad of Symptoms:

1. Hemolysis
2. Pancytopenia
3. Venous Thrombosis

Diagnosis: PNH may be diagnosed through specific laboratory investigations, even when all three symptoms are not present
initially.

Epidemiology:

Genetics: PNH is not inherited and is not considered a congenital disease.

Clinical Features:

● Common Symptoms: Hemoglobinuria (blood in urine), anemia, abdominal pain due to thrombosis, and possible
complications like Budd-Chiari syndrome.
● Survival Rate: Historically estimated at 10-20 years; complications include thrombosis, infections, and bleeding.

Diagnosis:

● Blood Tests: Shows normo-macrocytic anemia, elevated LDH, and low haptoglobin. Hemoglobinuria may be variable.
● Bone Marrow: Typically hypercellular with erythroid hyperplasia; may become hypocellular.
● Definitive Testing: Flow cytometry detects CD59 and CD55 deficiency on red cells, confirming increased
complement susceptibility.
Pathophysiology:

● Hemolysis occurs due to red cells' excessive sensitivity to complement activation, stemming from a mutation in the
PIGA gene, leading to a mix of mutant and normal cells.

Relationship to Aplastic Anemia (AA):

● Many PNH patients have a history of AA, suggesting a shared autoimmune pathogenesis.

Treatment:

● Historic Options: Limited to allogeneic BMT or supportive care.

● Current Treatments:
○ Eculizumab: Blocks complement component C5, reducing hemolysis and thrombosis.
○ Ravulizumab: A longer-acting alternative requiring less frequent dosing.
● Supportive Care: Includes folic acid, monitoring iron levels, and blood transfusions as needed.
● Anticoagulation: Recommended for patients with a history of thrombosis.
● Future Therapies: Investigational drugs targeting upstream complement activation are being studied.
Acute Due to
Acute Blood
Loss
Causes:

● External: Trauma, obstetric hemorrhage.

● Internal: Gastrointestinal bleeding, ruptured spleen, ectopic pregnancy, subarachnoid hemorrhage, aneurysm leakage.

Stages of APHA:

1. Initial Stage (Hypovolemia):

○ Blood volume loss occurs without immediate hemoglobin drop.
○ Symptoms: Tachycardia, tachypnea, pale/cold skin, reduced urine output.
○ Risks: Loss of consciousness, acute renal failure.
2. Emergency Response (Hemodilution):
○ Fluid shifts cause hemodilution, correlating anemia with blood volume lost.
3. Bone Marrow Recovery:
○ If bleeding stops, increased RBC production is reflected in elevated reticulocyte counts and erythropoietin levels.

Diagnosis:

● APHA is identified by a sudden hemoglobin drop.

● Signs of Bleeding:
○ Grey Turner Sign: Flank bruising (retroperitoneal bleeding).
○ Cullen Sign: Umbilical bruising (intraperitoneal bleeding).
○ Dullness on Chest Percussion: Indicates intrapleural bleeding.
● Additional investigations (imaging) may be necessary to locate the bleeding source.
TREATMENT

1. Stabilization:
○ Ensure airway, breathing, and circulation are prioritized.
○ Administer vasopressors if hypotension is present.
2. Blood Replacement:
○ Immediate Transfusion:
Blood transfusion is crucial due to the body’s inability to adapt to acute anemia.
○ Volume Expansion:
Use plasma for volume replacement to avoid diluting clotting factors.
3. Control Hemorrhage:
○ Identify and stop the source of bleeding.

Special Surgical Considerations:

● Significant blood loss can occur during surgeries; monitoring is essential.

● Preoperative autologous blood donation may be available.

Future Directions:

● Research is ongoing for blood substitutes, such as fluorocarbon synthetic chemicals and hemoglobin-based oxygen
carriers (HBOCs), but none have become standard treatments yet.
Bone Marrow
Failures
Types:

● Aplastic Anemia
● Myelodysplastic Syndrome (MDS)
● Pure Red Cell Aplasia (PRCA)
● Myelophthisis

Key Features:

● Hypoproliferative Anemia: A hallmark of these disorders.

● Pancytopenia: Commonly observed, characterized by decreased erythrocytes, leukocytes, and thrombocytes.

Pathophysiology:

● The reduction in blood counts arises from inadequate hematopoiesis rather than peripheral destruction of blood cells.

Etiologies of Marrow Dysfunction:

● Infectious agents
● Inflammatory processes
● Neoplastic conditions
1. Aplastic
anemia
Definition:

● Aplastic anemia is characterized by pancytopenia and bone marrow hypocellularity. It can be classified into:
○ Acquired Aplastic Anemia: Often due to external factors.
○ Iatrogenic Aplasia: Results from cytotoxic chemotherapy or other medical interventions.
○ Constitutional Aplastic Anemia: Genetic conditions such as:
■ Fanconi Anemia
■ Dyskeratosis Congenita
■ Telomere diseases
■ Hematologic manifestations linked to mutations in genes like GATA2, RUNX1, and MPL.

Epidemiology:

● Incidence rates vary globally:

○ Europe and Israel: Approximately 2 cases per million annually.
○ Thailand and China: Rates of 5 to 7 cases per million.
● Affects both genders equally, with a biphasic age distribution:
○ Major peak in teens and twenties.
○ Secondary peak in older adults.

Etiology:

● Most cases are idiopathic, but several clinical associations may suggest potential causes.
● Reliable differentiation of idiopathic cases from those with identifiable etiologies (e.g., drug exposure) is often challenging.
Etiologies

1. Radiation-Induced Aplasia: Caused by exposure to radiation, leading to DNA damage, particularly in mitotically active
tissues. Late effects may include MDS and leukemia, but not typically aplastic anemia.
2. Chemical Exposure:
○ Benzene: Strongly linked to aplastic anemia and leukemia; incidence correlates with cumulative exposure.
○ Other Chemicals: Limited evidence connecting other chemicals to marrow failure.
3. Drug-Induced Aplastic Anemia: Certain chemotherapeutic agents cause dose-dependent marrow suppression, while
idiosyncratic reactions to various drugs can lead to aplastic anemia.
4. Infectious Causes: Aplastic anemia can rarely follow viral infections like infectious mononucleosis.
5. Immunologic Conditions: Conditions such as graft-versus-host disease and systemic lupus erythematosus can be
associated with aplastic anemia.
6. Posthepatitis: Aplastic anemia may develop following seronegative hepatitis, presumed to be immune-mediated.
7. Pregnancy: Rarely occurs during pregnancy but may resolve post-delivery.
8. Paroxysmal Nocturnal Hemoglobinuria (PNH): PIG-A gene mutations can lead to aplastic anemia and PNH symptoms.
9. Constitutional Syndromes:
○ Fanconi Anemia: Autosomal recessive disorder with congenital anomalies and increased malignancy risk.
○ Diamond-Blackfan and Shwachman-Diamond Syndromes: Genetic defects in ribosome assembly and
hematologic presentation.
Genetic Factors

1. Constitutional Syndromes:
○ Fanconi Anemia: Involves defects in DNA repair, leading to chromosomal damage.
○ Telomeropathies: Mutations affect telomere repair, limiting cell proliferation.
2. Hematopoietic Gene Mutations:
○ Alterations in GATA and RUNX genes disrupt hematopoietic regulation.

Extrinsic Factors

1. Chemical and Drug Injury:

○ Exposure to high doses of radiation or toxic chemicals can damage the marrow. Idiosyncratic drug reactions may
occur due to altered drug metabolism, producing toxic intermediates like benzene metabolites.
2. Toxicity Mechanisms:
○ Genetic predispositions can increase susceptibility to drug-induced marrow failure.

Immune-Mediated Mechanisms

● Immune System Role:

○ Aplastic anemia may be immune-mediated, as evidenced by recovery in some patients treated with antilymphocyte
globulin (ALG).
○ Increased activated cytotoxic T-cell clones are found in patients, which decrease with immunosuppressive therapy.
○ Cytokines like interferon-γ (IFN-γ) can promote apoptosis in stem cells.
○ Loss of HLA expression in hematopoietic stem cells can lead to their abnormal expansion.
Clinical Features of Aplastic Anemia

History:

● Symptoms:
○ Bleeding: Easy bruising, gum bleeding, nosebleeds, heavy menstrual flow, petechiae.
○ Anemia: Fatigue, weakness, shortness of breath, tinnitus.
○ Infection: Rare as an initial symptom.
● General Condition: Patients may appear well despite low blood counts.
● Risk Factors: Previous drug use, chemical exposure, viral illnesses; family history of hematologic disorders or
telomeropathy.

Physical Examination:

● Skin: Petechiae, ecchymoses, pallor.

● Retinal Hemorrhages: May be present.
● Lymphadenopathy/Splenomegaly: Generally absent.
● Anomalies: Café au lait spots (Fanconi anemia), abnormal nails (dyskeratosis congenita), early hair graying (telomerase
defects).
Laboratory Studies in Aplastic Anemia
Blood Tests:

● Smear Findings:
○ Large erythrocytes, low platelets, and granulocytes; increased MCV; few or absent reticulocytes.
● Indicators:
○ Immature myeloid forms suggest leukemia or MDS; nucleated red blood cells indicate fibrosis or tumor invasion.

Bone Marrow Examination:

● Aspiration:
○ May show dilute smear; a “dry tap” indicates fibrosis.
● Biopsy:
○ Shows >75% fat; hematopoietic cells <25% of space; normal morphology of residual cells.

Ancillary Studies:

● Chromosome Breakage Studies: Exclude Fanconi anemia.

● Short Telomeres: Suggest telomerase or shelterin mutations.
● Flow Cytometry: Diagnoses PNH.
● Serologic Studies: Indicate recent viral infections; posthepatitis aplastic anemia is seronegative.

Genomics:

● Next-Generation Sequencing: Identifies pathogenic mutations; germline and somatic mutation panels assist in diagnosis.
Diagnosis of Aplastic Anemia

● Definition: Aplastic anemia is identified by pancytopenia and fatty bone marrow, mainly affecting adolescents and young
adults.
● Differential Diagnosis: Consider conditions like:
○ Splenomegaly from alcoholic cirrhosis
○ Metastatic cancer or systemic lupus erythematosus (SLE)
○ Miliary tuberculosis.
● Key Distinctions:
○ Constitutional vs. Acquired: Similar bone marrow morphology; family history and childhood blood abnormalities
suggest constitutional causes. Genomic testing can differentiate them, but results may take time.
○ Aplastic Anemia vs. MDS: Aplastic anemia may be mistaken for MDS, but MDS shows specific cell abnormalities
and cytogenetic changes.
● Immunologic Factors: Distinguishing between immune aplastic anemia and MDS can be difficult, as both may share
genetic mutations.
Treatment of Aplastic Anemia
○ Severe aplastic anemia is treated with stem cell transplantation or immunosuppression; glucocorticoids are
ineffective.

Hematopoietic Stem Cell Transplantation (HSCT):

○ Preferred for young patients with a compatible sibling donor, with high success rates (>90% for children).
○ Alternative sources include matched unrelated donors and umbilical cord blood.

Immunosuppression:

○ Standard treatment involves antithymocyte globulin (ATG) and cyclosporine, with 60-70% response rates.
○ Older adults may have increased risks.

Eltrombopag:

○ A thrombopoietin mimetic that improves response rates, especially when combined with ATG and cyclosporine.

Supportive Care:

○ Prompt infection management and transfusions for platelets and RBCs are critical.
○ Maintain platelet counts >10,000/μL and manage hemoglobin levels appropriately.

Overall Strategy:

○ Treatment should be individualized based on patient factors and disease severity.

 2.
Myelodysplastic
syndromes
Definition:
MDS are a group of hematologic disorders marked by:

● Cytopenias due to bone marrow failure.

● High risk of progression to acute myeloid leukemia (AML). Symptoms include anemia, thrombocytopenia, and neutropenia,
often with abnormal bone marrow characteristics.

Classification:
Originally classified by the French-American-British Cooperative Group, now refined by the WHO (2016) into several subtypes
based on:

● Blast percentages.
● Cytogenetic abnormalities.
● Somatic mutations.

Diagnosis:

● Diagnosis can be complex, requiring expert interpretation of clinical and pathological features.
● Reliable indicators include changes in megakaryocytes, while genomic testing aids in diagnosis but complicates
interpretation.

Epidemiology:

● Primarily affects older adults (mean age >70 years) with slight male predominance.
● Incidence: 35 to >100 cases per million in the general population; 30,000 to 40,000 new U.S. cases annually.
● Rare in children, often linked to genetic factors; secondary MDS can result from previous treatments at any age.
Etiology:

● Environmental Exposures: Linked to radiation and benzene; other risk factors are inconsistent.
● Secondary MDS: Develops as a late effect of cancer treatments (alkylating agents, DNA topoisomerase inhibitors).
● Genetic Factors: Can arise from conditions like acquired aplastic anemia; specific mutations (e.g., GATA2, RUNX1) may be
present.
● Aging: Primarily affects older adults due to accumulated mutations in hematopoietic stem cells.

Pathophysiology:

● Clonal Disorder: Characterized by disordered cell proliferation, impaired differentiation, and resulting cytopenias, with a risk
of leukemia.
● Genomic Instability: Approximately 50% of patients have cytogenetic abnormalities, often related to aging and specific
environmental exposures.
● Somatic Mutations: Over 100 recurrent mutations implicated; notable ones include SF3B1 (favorable outcome) and TP53
(poor outcome).
● Clonal Evolution: MDS evolves through mutations, leading to dominant clones.
● Hematologic Manifestations: Result from multiple genetic lesions affecting tumor suppressor genes and oncogenes.
● Immune Pathophysiology: Immune factors may play a role, especially in lower-risk MDS.
CLINICAL MANIFESTATIONS

● Primary Symptoms:
○ Anemia: Fatigue, weakness, dyspnea, pallor; many patients are asymptomatic, discovered through routine blood
tests.
● Historical Context:
○ Previous chemotherapy or radiation exposure is significant.
● Pediatric Considerations:
○ Rare in children, often linked to genetic conditions (e.g., Down syndrome, GATA2 mutations).
● Physical Exam Findings:
○ Signs of anemia; 20% may have splenomegaly.
○ Unusual skin lesions (e.g., Sweet’s syndrome) may be present.
● Constitutional Syndromes:
○ Specific anomalies in younger patients can indicate conditions like Fanconi anemia or telomeropathies.
LABORATORY FINDINGS

● Blood Tests:
○ Anemia: Present in most cases, often macrocytic.
○ Platelets: Typically large, may lack granules; functional issues can cause bleeding.
○ Neutrophils: Hypogranulated, with abnormal nuclei; may be functionally deficient.
○ White Blood Cell Count: Usually normal or low, except in CMML.
● Bone Marrow Findings:
○ Appearance: Generally normal or hypercellular; some cases may be hypocellular.
○ Common Morphological Changes:
■ Dyserythropoiesis with nuclear abnormalities and ringed sideroblasts.
■ Granulocyte precursors show hypogranulation and hyposegmentation.
■ Megakaryocytes may exhibit reduced numbers and disorganization.
● Prognostic Indicators:
○ Marrow Blasts: Proportion correlates with prognosis; should be counted manually and via flow cytometry.
○ Cytogenetics: Chromosomal abnormalities identified through cytogenetic analysis and fluorescence in situ
hybridization.
● Additional Notes: Clonal populations (e.g., PNH cells) and genetic testing for associated syndromes are important
considerations.
TREATMENT

Cure and Transplantation:

● Only hematopoietic stem cell transplantation offers a potential cure (~50% survival at 3 years).

Medications:

● Hypomethylating Agents:
○ Azacitidine: Improves blood counts in ~50% of patients; administered subcutaneously; main side effect is
myelosuppression.
○ Decitabine: 30-50% response rate; given as continuous IV infusion.
● Lenalidomide: Effective for 5q– syndrome; leads to transfusion independence; given orally.
● Immunosuppressants:
○ ATG and Cyclosporine: Effective for younger patients with refractory anemia; ~50% response rate.
● HGFs:
○ EPO: Improves hemoglobin levels; beneficial for patients with low serum EPO.
○ G-CSF: No survival benefit shown in trials.

Emerging Therapies:

● Luspatercept: Approved for MDS anemia; targets TGF-β suppression.

● Novel agents in trials include inhibitors targeting various genetic pathways.

Supportive Care:

● Blood transfusions are common; iron chelation needed to prevent secondary hemochromatosis.
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