SESSION TITLE: Medical Student/Resident Chest Infections Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Histoplasmosis infection is clinically silent in over 99% of immunocompetent individuals in endemic areas. If symptoms occur most are non-specific and self-limited. However, disseminated histoplasmosis can develop in immunocompetent patients with devastating consequences including significant mortality. CASE PRESENTATION: A previously healthy 45-year-old man presented after 2-3 weeks of worsening dyspnea, non-productive cough, and 20lb weight loss. Outpatient work up showed concern for atypical pneumonia, necessitating treatment with three escalating oral antibiotics showing no improvement prompting admission. He was transferred from an outside hospital intubated progressing toward ARDS requiring vasopressor support. On imaging there was diffuse bilateral peribronchovascular consolidation, groundglass opacities with septal thickening, hepatosplenomegaly, and retroperitoneal lymphadenopathy. Testing included respiratory viral panel positive for rhinovirus, fungitell, fungal blood cultures, urine antigens for histoplasmosis and blastomyces, and bronchoscopy. He was placed on broad spectrum antibiotics and itraconazole. The following day his fungal regimen was advanced to amphotericin B. Three days later his urine histoplasmosis antigen returned positive followed by a positive fungitell and lastly bronchoscopy cultures grew histoplasmosis. He required a month long hospital stay with aggressive ventilator support requiring tracheostomy, severe fevers requiring external cooling, and significant ATN that all slowly improved. Work up for an underlying etiology for possible immunosuppression was unrevealing. He was discharged to an extended care facility where he was liberated from the ventilator within a few days of hospital discharge with later tracheostomy decannulation. He remains on itraconazole 9 months later. He has returned to his regular activities. Most recent imaging shows mild scarring and residual consolidative and nodular opacities. DISCUSSION: Initial generalized symptoms and the rarity of disseminated histoplasmosis in immunocompetent patients can cause it to be overlooked on the differential, leading to significant delays in care. Further delays can occur as testing typically takes multiple days to result and may require bronchoscopy. In this case, a broad differential was considered with a decisive plan of starting the patient on amphotericin days prior to test results likely significantly improving overall prognosis. CONCLUSIONS: Timely diagnosis and treatment of disseminated histoplasmosis requires a broad differential diagnosis coupled with a high level of clinical suspicion. Aggressive treatment may need to begin prior to definitive diagnosis in patients with significant disease burden. Reference #1: Kauffman CA. Histoplasmosis: a clinical and laboratory update. Clin Microbiol Rev. 2007;20(1):115-132. doi:10.1128/CMR.00027-06 Reference #2: Ling Q, Zhu W, Lu Q, Jin T, Ding S. Disseminated histoplasmosis in an immunocompetent patient from an endemic area: A case report. Medicine (Baltimore). 2018;97(29):e11486. doi:10.1097/MD.0000000000011486 DISCLOSURES: No relevant relationships by Benjamin Ramser, source=Web Response No relevant relationships by Joy Wang, source=Web Response No relevant relationships by Steven Young, source=Web Response