Idiopathic pulmonary hemosiderosis

INTRODUCTION

Idiopathic pulmonary hemosiderosis is a rare disease found primarily in children that causes recurrent episodes of diffuse alveolar hemorrhage. Recurrent alveolar bleeding may eventually produce pulmonary hemosiderosis and fibrosis. Diffuse alveolar hemorrhage is characterized by hemoptysis, dyspnea, alveolar opacities on chest radiographs, and anemia and can result from a variety of underlying conditions (table 1). When no underlying cause for repeated episodes of diffuse alveolar hemorrhage is apparent, the entity is referred to as idiopathic pulmonary hemosiderosis (IPH) [1].

The clinical features, treatment, and prognosis of IPH will be reviewed here. A general discussion of the diffuse alveolar hemorrhage syndromes is provided separately. (See "The diffuse alveolar hemorrhage syndromes".)

PATHOGENESIS

The etiology of IPH is unknown. However, the response to immunosuppressive therapy suggests that immune processes may be involved. It appears that a structural defect in the alveolar capillaries, either in the alveolar basement membrane or in the alveolar endothelial cell, may predispose to the condition [1-5]. The accumulation of neutrophils in the alveoli also may play a role [6].

Immunologic abnormalities — The degree to which immunologic injury to the lung contributes to the development of IPH remains unclear. Immune complexes have been demonstrated in plasma in several patients; however, immunohistochemical examination of lung tissue generally has not supported an immunologic pathogenesis [2,3,7-10]. The possibility that autoimmune mechanisms play a role in IPH is suggested by the observation that approximately 25 percent of patients with the condition who survive for more than 10 years subsequently develop autoimmune disorders [11].

Links between IPH and ingested protein antigens have also been hypothesized, based upon the following observations: