Histoplasmosis

A 37-year-old man presented with fever, chills, myalgia, headache, and left-sided pleurisy of 2 weeks' duration. He also complained of weight loss and loss of appetite. The patient had recently returned from a family visit to Missouri.

He was taking no medications and had no known drug allergies. His temperature was 38.9°C (102°F). Mild ulceration of the oropharynx and dullness on percussion of the left lung base were found. A solitary, nonpruritic, nontender papule was noted on the thorax (A). The white blood cell count was elevated. A chest film revealed bilateral hilar adenopathy, a lung mass on the periphery of the left lung, and blunting of the left costophrenic angle (B).

Empiric ciprofloxacin therapy was given for 1 week without relief of symptoms. A fine-needle biopsy of the lung mass was performed; ovoid yeast forms of Histoplasma capsulatum were found (C). The patient's serum antibody titers to H capsulatum were positive in titers of 1:32. Bone marrow biopsy revealed intracellular yeast forms within reticuloendothelial cells; culture results were positive for H capsulatum (D).

The patient was treated with intravenous liposomal amphotericin B for 4 weeks. His symptoms resolved after 10 days of therapy.

Gopi Rana-Mukkavilli, MD of New York writes that histoplasmosis is the most common endemic systemic mycosis in the United States.¹H capsulatum is a dimorphic fungus that is prevalent in the Mississippi and Ohio river valleys. Patients unknowingly acquire this infection by inhaling the spores of the organism.

Histoplasmosis is associated with a variety of clinical symptoms. Dissemination occurs more frequently in immunocompromised patients, and multiple organ involvement ensues. Pulmonary infection is prevalent, and H capsulatum also can spread to the lymph nodes, bone marrow, liver, spleen, vitreous chamber of the eyes, and oropharynx. Diagnosis is made by detection of the ovoid yeast cells within tissue cultures.

Treatment is with antifungal agents such as amphotericin B, fluconazole, and ketoconazole. The prognosis is good if the diagnosis is made early and the infection has not disseminated.

REFERENCE:1. Bennett JC, Plum F, eds. Cecil Textbook of Medicine. 20th ed. Philadelphia: WB Saunders Company; 1996.