Adult respiratory distress syndrome due to malignant histiocytosis

While a 23-year-old man was being evaluated for a two-month history of night sweats, fever, and weight loss, he had the typical clinical, radiologic, and laboratory findings of adult respiratory distress syndrome (ARDS). After a diagnosis of malignant histiocytosis (MH) was established by lymph node biopsy, review of an earlier lung biopsy initially interpreted as nonspecific revealed malignant histiocytes. He failed to respond to combination chemotherapy and died as a result of progressive respiratory failure.