Basidiobolus ranarum as an etiologic agent of gastrointestinal zygomycosis.
Basidiobolus ranarum is a known cause of subcutaneous zygomycosis. Recently, its etiologic role in gastrointestinal infections has been increasingly recognized. While the clinical presentation of the subcutaneous disease is quite characteristic and the disease is easy to diagnose, gastrointestinal basidiobolomycosis poses diagnostic difficulties; its clinical presentation is nonspecific, there are no identifiable risk factors, and all age groups are susceptible. The case of gastrointestinal basidiobolomycosis described in the present report occurred in a 41-year-old Indian male who had a history of repair of a left inguinal hernia 2 years earlier and who is native to the southern part of India, where the subcutaneous form of the disease is indigenous. Diagnosis is based on the isolation of B. ranarum from cultures of urine and demonstration of broad, sparsely septate hyphal elements in histopathologic sections of the colon, with characteristic eosinophilic infiltration and the Splendore-Hoeppli phenomenon. The titers of both immunoglobulin G (IgG) and IgM antibodies to locally produced antigen of the fungus were elevated. The patient failed to respond to 8 weeks of amphotericin B therapy, and the isolate was later found to be resistant to amphotericin B, itraconazole, fluconazole, and flucytosine but susceptible to ketoconazole and miconazole. One other noteworthy feature of the fungus was that the patient's serum showed raised levels of Th2-type cytokines (interleukins 4 and 10) and tumor necrosis factor alpha. The present report underscores the need to consider gastrointestinal basidiobolomycosis in the differential diagnosis of inflammatory bowel diseases and suggests that, perhaps, more time should be invested in developing standardized serologic reagents that can be used as part of a less invasive means of diagnosis of the disease.