Fulminant disseminated histoplasmosis in a pediatric patient with ataxia-telangiectasia and autoimmune hepatitis: A diagnostic and therapeutic challenge.

Disseminated histoplasmosis (DH) is a common opportunistic mycosis in endemic regions, yet it remains underreported in pediatric patients with primary immunodeficiency or acquired immunosuppression. We present the clinical progression and fatal outcome of DH in a 12-year-old female from southeastern Honduras with an established diagnosis of Ataxia-Telangiectasia (AT) and Autoimmune hepatitis (AIH) managed with daily prednisone (1 mg/kg/day) and azathioprine (2 mg/kg/day), presented with fever, non-productive cough and progressive hypoxemic respiratory failure. Despite broad-spectrum antimicrobials, she rapidly developed severe acute respiratory distress syndrome (ARDS) and multi-organ dysfunction syndrome (MODS), culminating in irreversible cardiorespiratory arrest 24 h after ICU admission. Diagnosis of DH was confirmed via enzyme immunoassay (EIA) demonstrating high levels of antigenuria (15 ng/mL; threshold for high-level >5 ng/mL). This case highlights a critical therapeutic paradox where standard management for an autoimmune complication fully unmasked a lethal fungal infection in a vulnerable host. DH remains a notorious diagnostic mimicker in resource-limited settings where atypical presentation and delayed culture processing restrict timely polyene antifungal intervention. In endemic territories, proactive baseline screening for endemic mycoses and strict primary surveillance are mandatory before executing or maintaining intensive immunosuppression in pediatric patients with congenital immune dysregulation.