We report an unusual lethal complication of sickle cell anemia. The patient was admitted with a diagnosis of acute chest syndrome and died shortly after that of respiratory failure. Autopsy revealed numerous deposits of bone marrow hematopoietic tissue occluding the microvascular circulation of the lung. Many causes of acute chest syndrome in sickle cell anemia have been identified, including bone marrow infarction leading to embolism of bone marrow fat. However, the release of bone marrow hematopoietic tissue leading to pulmonary vascular occlusion is not generally recognized premortem by treating physicians.