Atypical disseminated cutaneous histoplasmosis in an immunocompetent child, caused by an "aberrant" variant of Histoplasma capsulatum var. capsulatum

Abstract

A case of atypical disseminated cutaneous histoplasmosis in a five-year old, otherwise healthy child, native and resident in São Paulo metropolitan area is reported. Cutaneous lesions were clinically atypical. Histologic examination disclosed a granulomatous reaction but no fungal structures could be demonstrated by specific staining nor by immunohistochemical reaction. The fungus was isolated from biopsy material on two different occasions, confirming diagnosis of an unusual fungal infection. The fungus, originally thought to be a Sepedonium sp. due to the large sized, hyaline or brownish colored tuberculated macroconidia and to lack of dimorphism (yeast form at 37 °C) produce H and M antigens, visualized by the immunodiffusion with rabbit anti-Histoplasma capsulatum hyperimmune serum. Patient’s serum sample was non reactive with H. capsulatum antigen by immunodiffusion, counterimmunoelectrophoresis and complement fixation tests, and immunoenzymatic assay failed to detect the specific circulating antigen. This serum was tested negative by double immunodiffusion when antigen obtained from one of the isolated samples was used. Both cultures were sent to Dr. Leo Kaufman, Ph.D. (Mycoses Immunodiagnostic Laboratory, CDC-Atlanta/USA), who identified them as H. capsulatum by the exoantigen and gen-probe tests. Both clinic and mycologic characteristics of the present case were atypical, suggesting the fungus isolated is an “aberrant variant” of H. capsulatum var. capsulatum, as described by SUTTON et al. in 199719. Treatment with itraconazole 100 mg/day led to cure within 90 days

Phylogeography of the fungal pathogenHistoplasma capsulatum

“…The Peruvian individuals had larger yeast cells than typical H. capsulatum and reminded mycologists of another fungal pathogen, Lacazia loboi , but clearly belong in the genus Histoplasma . Isolate H153 was also phenotypically distinct, having unusually large macroconidia, not converting to yeast at 37 °C and causing an atypical, disseminated cutaneous histoplasmosis (Lacaz et al . 1999).…”

Disseminated cutaneous‐only histoplasmosis in a patient with AIDS

“…These lesions most commonly develop on the face and chest, and presentation may also include oral erosions and ulcers. Very rarely, cutaneous lesions are the only manifestation . Most cases of disseminated histoplasmosis with reported cutaneous features have systemic symptoms, signs or radiological evidence to suggest the involvement of other organs …”