Sickle cell lung disease.

When a patient with sickle cell disease has fever and a lung infiltrate, usually it will be due to infection, even though cultures may be negative. However, pulmonary infarction can be virtually indistinguishable from pneumonia. Pneumonia is likely to be present in those younger than five years, with purulent sputum and upper lobe infiltrates. Coexisting crisis, a normal or low leukocyte alkaline phosphatase score and microangiopathic changes on peripheral blood smear favor thromboembolic disease. The fat embolism syndrome, caused by bone marrow necrosis and infarction, occurs in sickle cell disease.