ABSTRACT
The pathological features in the lungs of patients dying with sickle cell anemia reveal multiple mechanisms of injury.158,160,161 Pulmonary artery intimal proliferation and organized and recanalized thromboemboli are found. There may be widespread occlusion of small-and medium-sized arteries. In acute crisis, the vasculature may be packed with marrow elements, fat and sickled red cells along with inflammatory cells. In some patients, plexiform lesions are found in small pulmonary arterioles, along with eccentric intimal fibrosis and fibrinoid necrosis. These findings point to both acute and chronic changes, with additive and progressive occlusion of vessels, a hypertensive phenotype of the media, acute and chronic thrombosis in situ, and thromboembolism. It should be noted that pulmonary hypertension is seen with increased frequency in other hematological diseases associated with hemolysis, including pyruvate kinase deficiency and thalassemia, and is also found in diseases resulting in splenectomy.162-164 Thus, a role of free hemoglobin and iron may exist in the pathogenesis of chronic lung vascular injury and of platelet excess in situations where the spleen is dysfunctional. Both hemolysis and autosplenectomy are complications of sickle cell anemia.
