Idiopathic Pulmonary Hemosiderosis

To the Editor: Uda and Yashiro (June 8 issue)(1) report a case that they described as idiopathic pulmonary hemosiderosis. Although the imaging provides an illustrative example for which alveolar hemorrhage is an important etiologic consideration, we wish to highlight additional critical steps in the evaluation of children with these imaging findings - namely, lung biopsy and genetic testing. Idiopathic pulmonary capillaritis has a clinical presentation similar to that of idiopathic pulmonary hemosiderosis; however, the histologic findings and recommended treatment vary considerably.(2) Idiopathic pulmonary capillaritis is similar to microscopic polyangiitis in appearance, with neutrophils lining the pulmonary capillaries and fibrinoid necrosis. . . .