Hematuria Due to Possible Histoplasma-Associated Urinary Bladder Pseudotumor With Negative Serologic and Urine Antigen Testing

Abstract

Histoplasma capsulatum is a ubiquitous dimorphic fungus causing multiple infectious syndromes, ranging from subclinical to severe disseminated disease. We present an unusual case of hematuria due to pedunculated urinary bladder mass in an immunocompetent host. Although the gold standard for diagnosis of histoplasmosis is through demonstration of characteristic yeast forms on histopathologic examination of infected tissue, or observation of typical mycelial growth in culture of clinical specimens, investigational multiplex polymerase chain reaction of formalinized tissue was helpful in this case due to conflicting serologic testing, equivocal morphologic findings on histopathologic examination and, surprisingly, a negative urine Histoplasma antigen despite anatomically proximal location within the urinary bladder. Although antigen immunoassay and serology are commonly used proxy diagnostics in Histoplasma-associated disease, varying performance characteristics in certain disease states, such as cases of locally proliferative infection mimicking neoplastic growth similar to this report, may lead to elusive diagnosis.