Multiple unusual lung etiologies in a child with acute lymphocytic leukemia.

Granulomatous lung disease is a rare and perplexing differential in pediatrics. Pulmonary Cryptococcus falls into the differential but is not high on the list, particularly in a non-AIDS patient. Methotrexate (MTX) is a commonly used agent for chemotherapy in oncology and has been documented to cause lung injury in both patients with rheumatologic and oncologic diseases. Our patient had chronic cough and then developed an opportunistic infection resulting in respiratory failure. Lung biopsy showed two underlying unusual diagnoses: MTX lung injury and cryptococcal pneumonia. His case is presented with particular attention to his prolonged road to diagnosis.