A Case Report of Disseminated Histoplasmosis in AIDS Diagnosed Through Peripheral Blood Smear

Histoplasma capsulatum is an environmental fungus that causes opportunistic infections in AIDS patients in endemic areas but is uncommon in Europe. It shares clinical features with other opportunistic infections and lymphoproliferative disorders common in AIDS patients. The World Health Organization included Histoplasma antigen tests on the Lists of Essential In Vitro Diagnostics, however, they are not routinely available in non-endemic countries. Consequently, mycoses can be a great challenge for clinicians in non-endemic countries.

We report the case of a 42-year-old Colombian woman admitted to an Italian university hospital with diarrhea, acute renal failure, psychomotor impairment and fever. When a screening HIV test came back positive, she was screened for opportunistic infections with no results. Given the severity of her clinical condition a broad spectrum antibacterial and antifungal therapy was started in addition to HAART. A blood smear documented leucocytes inclusions, identified as capsular structures. On suspicion of Histoplasma capsulatum the patient was started on empiric amphotericin B. The diagnosis was confirmed by positive serology. Despite therapy, the patient died shortly after. In the following days, the mycology laboratory managed to grow Histoplasma capsulatum, thus confirming the diagnosis of invasive histoplasmosis in AIDS.

The case highlights the need for a high index of suspicion for the diagnosis of endemic mycosis outside of endemic areas, and the necessity of expanding access to tests. Even if antigen/ antibody tests are not available, however, blood smear has worldwide feasibility and allows a rapid diagnosis.