ACTINOMYCOSIS AND SARCOIDOSIS
ACTINOMYCOSIS
Actinomycosis is a long-lasting (chronic) pus-forming disease caused by anaerobic bacteria
called Actinomyces israelii. Although the name suggests a fungus, it is actually a filamentous
bacterium, not a true fungus.
- The disease occurs worldwide.
- The bacteria normally live as commensals in the mouth, intestine, and vagina.
- Infection is endogenous (from the person’s own flora) and does not spread by person-to-
person contact.
- It occurs when bacteria enter tissues through breaks in the mucosa or in association with
other diseases.
MORPHOLOGIC FEATURES
Depending on the site of infection, actinomycosis is of 4 main types:
1. Cervicofacial Actinomycosis
- Most common (60%) and has the best prognosis.
- Infection usually starts after dental problems like tonsillitis, caries, periodontal disease, or
tooth extraction trauma.
- A firm swelling develops in the lower jaw (“lumpy jaw”).
- Later, it breaks down forming abscesses and draining sinuses.
- Pus contains yellow “sulphur granules” (tiny bacterial colonies).
- Infection can spread into soft tissues and even destroy bone.
2. Thoracic Actinomycosis
- Infection occurs in the lungs due to aspiration from the mouth or spread from
abdomen/liver.
- Initially looks like pneumonia, but later spreads to lungs, pleura, ribs, and vertebrae.
3. Abdominal Actinomycosis
- Usually affects appendix, caecum, and liver.
- Caused by swallowing organisms from the mouth or spread from thoracic cavity.
4. Pelvic Actinomycosis
- Occurs in women using intrauterine contraceptive devices (IUCDs).
Microscopic Features
1. Inflammatory reaction is a granuloma with central pus (suppuration). Abscess forms in
the centre, surrounded by chronic inflammatory cells, giant cells, and fibroblasts.
2. The abscess centre has bacterial colonies called sulphur granules, appearing as radiating
filaments with club-shaped ends.
3. On staining: Gram-positive filaments, non-acid fast, positive with Gomori’s methenamine
silver (GMS) stain.
SARCOIDOSIS (BOECK’S SARCOID)
Sarcoidosis is a multisystem disease of unknown cause.
- Affects mainly young adults (20–40 years).
- May be asymptomatic or cause problems in lungs, lymph nodes, skin, eyes, liver, spleen,
salivary glands, and bones of hands/feet.
- Main feature is non-caseating granulomas (called sarcoid granulomas).
ETIOLOGY AND PATHOGENESIS
Exact cause is unknown. The disease involves immune disturbance, genetic tendency, and
environmental exposure.
1. Disturbed Immune System
- Macrophages present an unknown antigen to helper T-cells.
- These cells release cytokines (IL-2, IFN-γ, IL-8, IL-10, IL-12, IL-18, TNF).
- Cytokines form granulomas: mainly macrophages + some T-cells.
2. Genetic Predisposition
- Higher risk in people with certain HLA types: HLA-DRB1, HLA-A1, HLA-B8.
3. Environmental Agent
- Exact trigger unknown. Possible suspects: mycobacteria, Propionibacter acnes, rickettsia,
atypical mycobacteria.
KVEIM’S TEST
- A diagnostic intradermal test.
- Antigen from sarcoid lymph node/spleen is injected under the skin.
- In 3–6 weeks, a small nodule forms. On biopsy, it shows non-caseating granulomas.
MORPHOLOGIC FEATURES
Sarcoidosis can affect many organs, but lungs and lymph nodes are most commonly
involved.
Microscopic Features
1. Non-caseating sarcoid granulomas composed of epithelioid cells, Langhans’ giant cells,
foreign body giant cells, surrounded by fibroblasts. Sometimes fibrinoid necrosis is seen.
2. Granulomas are usually “naked” with very few lymphocytes.
3. Late stage: granulomas become hyalinised fibrous tissue.
4. Giant cells may contain:
- Asteroid bodies (star-shaped eosinophilic structures)
- Schaumann’s bodies (concentric calcium and iron deposits)
- Birefringent crystals (colorless, seen under polarised light)
(Similar inclusions also seen in chronic beryllium disease).
