CASE PRESENTATION: A 6-year-old previously healthy male presented with fever, cough and hypoxia. Initial Chest X-ray demonstrated diffuse pulmonary opacities and chest CT showed bilateral air space and interstitial opacities without evidence of bronchiectasis, air trapping or cavity. Laboratory assessment revealed mild eosinophilia (2090/uL). Bronchoscopy revealed BAL eosinophilia (42%). Patient was diagnosed with acute idiopathic eosinophilic pneumonia and placed on systemic steroids.1 Within 24 hours he had resolution of symptoms, hypoxia and peripheral eosinophilia. At 2-week follow-up, fungal IgG was elevated for Histoplasmosis (1:32) and Aspergillus (1:16). Chest x-ray was unchanged. Given return of fevers, fatigue and intermittent tachypnea, he received pulse IV steroids without clinical improvement. Repeat Histoplasmosis titers increased to 1:128 and he was placed on IV Liposomal Amphotericin B for presumed Pulmonary Histoplasmosis. Repeat bronchoscopy with BAL revealed resolution of eosinophilia and both BAL galactomannan (2.01) and Aspergillus fumigatus PCR were positive. The patient was transitioned to IV Voriconazole for broader antifungal coverage. After 1 week of therapy without improvement, a lung biopsy was obtained. Silver staining was consistent with pulmonary aspergillosis and Aspergillus fumigatus was subsequently cultured. Immune evaluation revealed a Dihydrorhodamine-123 Chronic Granulomatous Disease (CGD) assay with a mean fluorescence index of 11, consistent with autosomal recessive CGD. Genetic testing was positive for the NCF1 gene, confirming the diagnosis.