373. Immune Reconstitution Inflammatory Syndrome in Patients with HIV/AIDS and Histoplasmosis: A Case Series

Abstract Background Immune Reconstitution Inflammatory Syndrome (IRIS) in HIV infection is the unexpected clinical deterioration due to worsening (paradoxical) or uncovering (unmasking) of an infection or malignancy upon initiation of antiretroviral therapy (ART). Histoplasma capsulatum (H. capsulatum) is the most common endemic mycosis in patients with AIDS, usually manifesting as disseminated disease at CD4 counts < 150 cells/μl. In the ART era, histoplasmosis IRIS has been described in case reports, but there has been a limited description regarding clinical presentations and pathogenesis in the United States. Methods ART-naive HIV+ patients with a CD4+ T-cell count < 100 cells/µL enrolled in prospective studies at the National Institutes of Health (NIH) (NCT00286767, NCT02147405) were evaluated to identify those with histoplasmosis and followed after ART initiation to identify those who would eventually develop IRIS. Results From a total of 271 patients, we identified 9 patients with histoplasmosis. The median age, CD4+ count and HIV VL of these 9 patients was 36 years, 40 cells/mm3 and 193,184 copies/mL, respectively. Two patients developed IRIS only to histoplasmosis (1 unmasking and 1 paradoxical), 2 patients developed IRIS to both histoplasmosis and nontuberculous mycobacteria (NTM) and 3 patients developed IRIS to other infections (1 VZV, and 2 NTM). The manifestations of histoplasmosis IRIS in our cohort ranged from worsening lymphadenopathy to small bowel obstruction and worsening pulmonary symptoms. Conclusion Histoplasma-related IRIS can present with worsening lymphadenopathy, small bowel obstruction, and worsening pulmonary symptoms. The emergence of IRIS appears to be very common in people with HIV and disseminated histoplasmosis but the underlying trigger may be histoplasma, other co-infections or both. Disclosures All authors: No reported disclosures.