*Purpose: Histoplasmosis is responsible for the greatest number of hospitalizations and deaths due to endemic mycoses in the United States. Although lying near the western edge of the “histo belt,” our center has observed an increased number of cases of histoplasmosis among its kidney transplant (KT) recipients recently. This study aimed to identify patient characteristics warranting further investigation in hopes of identifying certain populations that would benefit from antifungal prophylaxis or screening.

*Methods: We performed a retrospective review of all new cases of histoplasmosis diagnosed in KT recipients from 2010 through 2018 at our center. Cases of histoplasmosis were defined as disease-compatible clinical manifestations in the setting of positive histopathologic, serologic, or antigenic testing. Demographic and clinical data were collected.

*Results: 41 cases of histoplasmosis were identified, approximately 4.5 cases per year. Of these, 35 cases were disseminated, 4 cases were pulmonary, one was isolated to the central nervous system, and one was donor derived and isolated to the allograft. The mean patient age was 51. 54% of patients were male and 88% of patients were white. 27% of patients lived in rural areas as defined by the United States Census Bureau, and only 12% reported an agricultural career. Urine antigen testing was the most utilized diagnostic test and was found to be positive in 90% of cases while serum antigen testing was positive in 82% of cases. Only 10 cases of histoplasmosis were diagnosed within the first year following transplant. Median duration of treatment was 1 year but 7% of patients relapsed once off treatment, 17% have ongoing treatment, and 10% died while receiving treatment.

*Conclusions: Growing numbers of cases of histoplasmosis among KT recipients may represent an increasing incidence in the disease, increased testing for it, or a shift in its endemicity. Regardless, histoplasmosis is a source of significant morbidity and mortality among our KT population. Relatively few subjects exhibited classic risk factors of rural residence and agricultural employment. These observations suggest that classic risk factors may not be as relevant in immunosuppressed populations. Contrary to previous studies, only a minority of our subjects developed histoplasmosis in the first year following transplant. Thus prophylaxis, if indicated in a subset, may need to be given indefinitely. Further studies of KT patients may better characterize who might benefit from prophylaxis or screening.

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