A patient presents with erythematous, indurated lesions on the face and extremities that are ulcerated and discharging pus accompanied by low-grade fever, chest pain, cough and hemoptysis. What’s your diagnosis?
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North American blastomycosis, also known as blastomycetic dermatitis and Gilchrist’s disease, is a fungal infection caused by Blastomyces dermatitidis. Endemic in certain parts of the United States, including the Mississippi and Ohio river basins and the Great Lake region, infection occurs when the fungus is inhaled from it’s natural soil habitat. Incidence of the disease is rare, with the CDC reporting 1.4 cases per 100,000 people in Wisconsin from 1986 to 1995.
Signs and symptoms of the disease are varied and can range from an acute illness resembling pneumonia, a chronic illness sometimes mistaken for tuberculosis or skin cancer, or a rapidly progressive disease manifesting as acute respiratory distress syndrome.
Although blastomycosis is chiefly a pulmonary disease, disseminated forms of infection often involve skin lesions that present as papules or nodules. Erythematous indurated areas with chancres usually appear within one to two weeks of inoculation, accompanied by lymphangitis and lymphadenopathy. These enlarge over time to form hyperkeratotic lesions, often with central scarring or ulceration. Infection may also affect other sites including the bones and central nervous system.
Diagnosis & Treatment
Clinicians can confirm blastomycosis by identifying broad-based budding B. dermatitidis organisms in sputum or tissue samples using KOH prep, cytology or histology.
Itraconazole (Sporonax) 200-400 mg daily for six months is recommended for less severe infections. For widespread disseminated blastomycosis in patients who are critically ill, clinicians can consider amphotericin B (up to 1mg/kg daily). Ketoconazole has also been used as an alternative therapy.
1. Fitzpatrick’s Dermatology in General Medicine (5th ed.). 1999. New York: McGraw-Hill.
Centers for Disease Control and Prevention. MMWR Morb. Mortal. Wkly. Rep. 45 (28): 601-3.