Blastomycosis is a systemic infection caused by the biphasic fungus Blastomyces dermatitidis. Although initially believed to be confined to certain parts of North America, it has recently been reported in Canada, Africa, Israel, Eastern Europe and Saudi Arabia.
Blastomycosis primarily involves the skin, where it presents as non-itchy papular lesions that later develop into ulcers with red verrucous margins. The ulcers are initially confined to the exposed parts of the body but later involve the unexposed parts as well. Atrophy and scarring may occur. Pulmonary involvement presents as a solitary lesion resembling a malignancy or gives rise to radiological features similar to the primary complex of tuberculosis. Systemic symptoms such as fever, malaise, cough and weight loss are usually present. Bone lesions are common and present as painful swellings.
The diagnosis is confirmed by demonstrating the organism in histological sections or by culture. Serology is not useful because of the marked cross-reactivity of antibodies to Blastomyces with Histoplasma.
The drug of choice is amphotericin.
Invasive zygomycosis, mucormycosis, is rare and is caused by several fungi, including Mucor, Rhizopus and Absidia. It occurs in ill patients. The hallmark of the disease is vascular invasion with marked haemorrhagic necrosis. Rhinocerebral mucormycosis is the commonest form. Nasal stuffiness, facial pain and oedema, and necrotic, black nasal turbinates are characteristic. It is rare and is mainly seen in diabetics with ketoacidosis. Other forms include pulmonary and disseminated infection (immunosuppressed), gastrointestinal infection (in malnutrition) and cutaneous involvement (in burns). Treatment is with amphotericin. This condition is invariably fatal if left untreated.
Candidiasis is the most common fungal infection in humans and is caused by Candida albicans. Candida are small asexual fungi. All the species that are pathogenic to humans are normal oropharyngeal and gastrointestinal commensals. Candidiasis is found worldwide.
Practically any organ in the body can be invaded by Candida, but vaginal infection and oral thrush are the commonest forms. This latter is seen in the very young, in the elderly, following antibiotic therapy and in those who are immunosuppressed. Candidal oesophagitis may present with painful dysphagia. Cutaneous candidiasis typically occurs in intertriginous areas. It is also an important cause of paronychia. Balanitis and vaginal infection are also common.
CHRONIC MUCOCUTANEOUS CANDIDIASIS is a rare manifestation, usually occurring in children, and is associated with aT-cell defect. It presents with hyperkeratotic plaque-like lesions on the skin, especially the face, and on the finger-nails. It is associated with several endocrinopathies, including hypothyroidism and hypoparathyroidism. Less commonly dissemination of candidiasis may lead to haematogenous spread, with meningitis, pulmonary involvement, endocarditis or osteomyelitis.
The fungi can be demonstrated in scrapings from infected lesions or in tissue secretions.
This varies depending on the site and severity of infection. Oral lesions respond to nystatin, oral amphotericin or miconazole. For more severe systemic infections, parenteral therapy with amphotericin or ketoconazole, or oral therapy with flucytosine 50-75 mg kg-l daily for 2- 3 weeks may be required.