Unusual Clinical Presentation and Histologic Findings of Disseminated Histoplasmosis in an AIDS Patient With Thickly Crusted Facial Nodules

Abstract

Histoplasma capsulatum is a pathogenic dimorphic fungus with infection most often occurring in Midwestern United States and Central America where the organism is endemic. Pulmonary histoplasmosis in a host with normal immunity usually has minimal symptoms and occurs after inhalation of tuberculated macroconidia. Impaired cellular immunity, associated with HIV positivity, greatly increases the risk for dissemination via hematogenous spread in macrophages either after primary exposure or due to reactivation of dormant pulmonary lesions. HIV-positive patients with CD4 counts less than 150/μL are at greatest risk for dissemination. Cutaneous lesions without pulmonary symptoms may represent the initial manifestation of disseminated disease. We report a case of a 31-yearold Hispanic man with CD4 count of 46/μL presenting with dizziness and fever. Physical examination revealed thickly crusted nodules on the bridge of the nose and cheeks; lungs were clear to auscultation bilaterally. Histologic findings in a cheek biopsy revealed necrotizing granulomas and mixed inflammatory infiltrate of neutrophils, plasma cells, and histiocytes. Silver and PAS stains showed innumerable budding yeasts. A diagnosis of deep fungal infection was made with a differential diagnosis including blastomycosis. Two weeks later a biopsy of the right lower lobe revealed histiocytes and rare small oval yeasts. The skin biopsy was pulled for review. Using an ocular micrometer, the narrow-based budding yeasts measured 4-5 μm in both skin and lung biopsies. A diagnosis of histoplasmosis was made. Histoplasma urinary antigen was recommended. This case study highlights the necessity of using an ocular micrometer to carefully measure fungal forms in all locations when encountered in an immunocompromised patient. Tissue reactions may be unusual. Correct organism identification is important so that appropriate antifungal agents can be administered. In cases of disseminated histoplasmosis, manual review of peripheral blood smears may reveal fungal forms in monocytes and neutrophils.