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Blastomycosis

Alternative names : - North American blastomycosis; Gilchrist's disease

Also called Gilchrist's disease, blastomycosis is caused by the yeast like fungus Blastomyces dermatitidis, which usually infects the lungs and produces bronchopneumonia. Less frequently, this fungus may disseminate through the blood and cause osteomyelitis and central nervous system (CNS), skin, and genital disorders.

Untreated blastomycosis is slowly progressive and usually fatal; however, spontaneous remissions occasionally occur. With anti fungal drug therapy and supportive treatment, the prognosis for patients with blastomycosis is good.

Causes

Signs and symptoms

Initial clinical indicators of pulmonary blastomycosis mimic those of a viral upper respiratory tract infection. These findings typically include a dry, hacking, or productive cough (occasionally hemoptysis), pleuritic chest pain, fever, shaking, chills, night sweats, malaise, anorexia, and weight loss.

• Cutaneous blastomycosis causes small, painless, nonpruritic, and nondistinctive macules or papules on exposed body parts. These lesions become raised and reddened and occasionally progress to draining skin abscesses or fistulas.
• Skeletal involvement causes soft tissue swelling, tenderness, and warmth over bony lesions, which generally occur in the thoracic, lumbar, and sacral regions; long bones of the legs; and, in children, the skull.
• Genital involvement produces painful swelling of the testes, the epididymis, or the prostate; deep perineal pain; pyuria; and hematuria.
• CNS involvement causes meningitis or cerebral abscesses, resulting in a decreased level of consciousness (LOC), lethargy, and change in mood or affect.

Other dissemination may result in Addison's disease (adrenal insufficiency), pericarditis, and arthritis.

Diagnosis

Various tests may be ordered to diagnose blastomycosis, including:

• culture of B. dermatitidis from skin lesions, pus, sputum, or pulmonary secretions
• biopsy of tissue from the skin or lungs or of bronchial washings, sputum, or pus, as the doctor finds appropriate
• complement fixation testing. Although such testing isn't conclusive, a high titer in extrapulmonary disease is a poor prognostic sign.
• immunodiffusion testing. This specific study detects antibodies for the A and B antigen of blastomycosis.

In addition, suspected pulmonary blastomycosis requires a chest X-ray, which may show pulmonary infiltrates. Other abnormal laboratory findings include an increased white blood cell count and erythrocyte sedimentation rate, slightly increased serum globulin levels, mild normochromic anemia and, with bone lesions, an increased alkaline phosphatase level.

Treatment

Prevention

Avoiding travel to areas where the disorder occurs will prevent exposure, but this is not practical for most people. Although other prevention is unknown, the disorder is rare except in people who are immunosuppressed .