FUNGAL INFECTION (MYCOSES)

- There are three groups of fungi which causes human disease

 Multinucleate branched filamentous (moulds) e.g trichophyton

 Round or ovoid single cells as yeast e.g Cryptococcus neoformans
 Dimorphic fungi that have certain of the growth characteristics of both e.g
candida albucans.

- Certain fungi cause only superficial infections while others can cause invasive
disease.
- Fungi like Candida can cause both superficial and deep infection.
- Some fungi are opportunistic and will not normally invade unless the defense
mechanisms are impaired, as in an immunocompromised host.
- Fungi infections are transmitted by spores or hyphae and normally enter the body
through the lungs or the skin, where they may cause disease, or from where they may
disseminate to other parts of the body.
- Fungal infections tend to be chronic, and often required prolonged chemotherapy.
- For some infections there is still no effective treatment.
- Fungi also cause disease through allergy and from toxins such as ergot, muscarine
and aflatoxin.

SUPERFICIAL
1. DERMATOPHYTOSIS
Tinea infections, Ringworm

- They are due to infection by dermatophyte fungi.

- There are three main genera:-

 Trichophyton that cause skin, hair, and nail infections.

 Microsporum that cause skin and hair infections.
 Epidermophyton that cause infection of skin and nails

- These organisms grow in the soil and on animals produce a number of diverse and
characteristic clinical lesions.
- Dermatophytes invade keratin only
- In general, zoophilic fungi cause a more severe but short-lived inflammatory response
than anthropophilic (spread from person to person)

TINEA CAPITIS

- Occurs in children and is only rarely seen in infant and adults.

- It is a dermatophytosis of the scalp characterized by asymptomatic, often hairless
patches of skin associated with mild erythema, crust formation and scale.

Fungal infections
TINEA CORPORIS

- It is a common superficial fungi infection of the body surface that affects persons of
all ages, but particularly children.

- Predisposing factors include

1. excessive heat and humility.

2. exposure to infected animals.
3. and chronic dermatophytosis of the feet or nails

- The most common type of tinea corporis is an expanding, round, slightly

erythematous plaque with an elevated scaling border.

TINEA CRURIS

- Occurs most frequently in the inguinal areas obese men during warm weather.
- Heat, friction, and maceration all predispose to its development.
- The infection usually first appears on the upper inner thighs, with gradual extension
of moist, red patches that have raised scaling borders

TINEA PEDIS (athlete’s foot)

- Affects about 40% of the population at some times in their lives.

- There is diffuse erythema and scaling, often initialy localized to the web spaces.
- Most of the inflammatory tissue reaction, however, has been shown recently to be due
to bacteria super infection and not directly related to the primary dermatophytosis
- It may spread to the nail.

TINEA VERSICOLOR

- Occurs on the upper trunk and highly distinctive in appearance.

- The lesion consists of groups of macules of all sizes, lighter or darker than
surrounding skin with a fine peripheral scale
- It is caused by Malassezia furfur

CANDIDIASIS

- Also called Candidosis or Moniliasis

- It is caused by Candida albicans, a yeast.
- It is the commonest fungus of medical importance.
- It is ubiquitous in the environment but it may be transmitted between people directly.
- Candidiasis is usually a superficial infection of skin, nails or mucous membrane with
the yeast form of the fungus, causing mild inflammation.
- Factors that predispose to candidiasis include:-

Fungal infections
 (A) Loss of integrity of skin and mucosae
* Maceration of skin due to climate or obesity
* Eczema
* Dentures
(B) Encouragement of local multiplication of candida
* Alteration of mucosal flora eg due to antibiotic treatment
* Hormonal: diabetes, pregnancy
(C) Suppression of inflammatory and immune response
* Specific congenital T lymphocyte defect.
* Leucopenia of any cause.
* Immunosuppressive drugs including topical corticosteroids
* Malignancy
* HIV infection

- Infections of the skin may resemble those caused by other dermatophytes but are
commonest where the skin is moist and in contact with itself e.g groin, perineum,
breast, axillae.
- Nail infections start at the base, forming ridges, often accompanied by paronychia.
- In the mouth, white curd-like patches are seen which can be scraped away leaving a
bleeding base.
- Atrophy of the gums and angular stomatitis are common in the elderly.
- Candida vaginitis causes intense pruritus and a thick creamy discharge.
- In children affected by muco-cutaneous candidiasis there is widespread involvement
of skin, nails, hair and mucosae which is disfiguring and responds poorly to
treatment.
- Systemic candidiasis may present as septicaemia or with the features of an infection
of oesophagus, gastrointestinal tract, heart, lungs, urinary tract or brain meninges.

ASPERGILLOSIS
- It is a common respiratory mycoses
- Most cases of broncho-pulmonary asperigillosis are caused by Aspergillus fumigatus,
but other members of the genus (A clavatus, A. flavus, A. niger and A. terreus)
occasionally cause disease.

- The conditions associated with aspergillus species include:-

 Allergic asthma
 Allergic broncho-pulmonary aspergillosis (asthmatic pulmonary eosinophilia).
 Extrinsic allergic alveolitis.
 Intracavitary aspergilloma.
 Invasive pulmonary aspergillosis

Allergic Bronchopulmonary Aspergillosis(ABPA)

- Caused by hypersensitivity reaction to A fumigatus involving the bronchial wall and

peripheral parts of lung.
- In the vast majority of patients it is associated with bronchial asthma, but it can occur
in non-asthmatics.

Fungal infections
 - It is a reconginized complication of cystic fibrosis
- It is one of the causes of pulmonary eosinophilia
- Fever, breathlessness, cough productive of bronchial casts and worsening of
asthmatic symptoms can all be manifestations of ABPA
- Repeated episodes can cause bronchiectasis, and its (bronchiectasis) symptoms and
complications can overshadow those of asthma.

Intracacitary Aspergilloma

- Inhaled air-borne spores of A. fumigatus may lodge and germinate in damaged

pulmonary tissues and an “aspergilloma’’ (a ball aspergillus fungus) can form in any
area of damaged lung in which there is a persistent abnormal space.
- The most common cause of such pulmonary damage is tuberculosis, but aspergilloma
can develop in an abscess cavity, a bronchiectatic space or even a cavitated tumour.
- Apergilloma may be responsible for recurrent haemotysis which is often severe in the
patients

Invasive Pulmonary Aspergillosis

- Invasive of a previously health lung by A. fumigatus is uncommon but can produce a

serious and often fatal condition which usually occurs in patients who are
immunocompromised either by drugs or disease.

- The source of the infection can be an aspergilloma.

- Spread of the disease throughout the lungs is usually rapid with the production of
consolidation necrosis and cavitation.

- The formation of multiple abscesses is associated with the production of copious

amounts of purulent sputum which is often blood-stained.

MYCETOMA (MADURA FOOT)

- Even though it is classified as a subcutaneous mycoses, it is a chronic fungal infection

of deep soft tissue and bones, most commonly of the limbs, but also infect abdominal
organs or chest wall or head

- It is produced by members of two groups of organisms classified as Eumycetes and

aerobiv Actinomycetes

- A feature common to both groups is the formation of grains which are colonies of
matted organism with characteristic colours, ranging from 60 microns to 3mm in
diameter.

- The incidence is related to climate, being especially high when an arid hot season
ends in rains.

- The histology is that of a chronic granuloma with a fibrous stroma and cyst-like
spaces in which lie the characteristic grains.

- The fungus is usually introduced by a thorn and the infection is common in the foot.
Fungal infections
 - The mycetoma begins as a painless swelling, and eventually penetrates bone.

- Nodules develop under epidermis and these rupture revealing sinuses through which
grains are discharged. Some sinuses may heal with scarring while fresh ones appear
elsewhere.

MUCORMYCOSIS
- This is caused by Rhizopus oryzae (mucororyzae)

- It is a zygomycete fungus which has characteristically wide, branching hyphae up to

25mm across.

- Virtually all victims of mucormycoses are patients with uncontrolled diabetes

mellitus in a state of ketoacidosis.

- The primary site infection is the nasal turbinates.

- The clinical features involve sinusitis inflammation of the orbit with proptosis and
meningo-encephalitis, resulting from invasion of the fungus through the cribriform
plate.

- Rhizopus induces a florid acute inflammatory reaction and causes extensive necrosis.

- Further tissue damage results from its propensity to invade blood vessel walls with
consequent thrombosis

- Cavernous sinus thrombosis and pituitary infarction are commonly seen in fatal cases.

- Mucormycosis is the most fulminant of all mycoses, death usually occurring within a
few days of diagnosis.

Fungal infections