CASE PRESENTATION: 68 year-old male with acute myeloid leukemia presents with dypsnea, hypoxemia and fevers after completion of experimental chemotherapy which included cytarabine. Physical examination revealed new oxygen requirement, decreased breath sounds from mid to lower left lung field with dullness to percussion. Further workup showed pancytopenia, LDH 368, BNP 90. Imaging revealed a left pleural effusion, bilateral ground glass opacities, and infiltrates. A left sided chest tube and bronchoscopy with bronchoalveolar lavage were completed. Microbiologic examination of bronchoalveolar fluid revealed positive pneumocystis pneumonia PCR, beta-d-glucan level >500, and cytology revealing histiocytes and abundant granular proteinaceous material, positive by periodic acid-Schiff staining.