Pulmonary involvement in unusual multisystem disorders.

The clinical syndrome of interstitial lung disease encompasses a number of clinical disorders that affect the alveolar walls, interstitium, and vicinal structures including small airway and pulmonary vasculature. The syndrome has more than 200 causes including bacterial, viral, fungal, protozoal, and parasitic infections; collagen vascular disorders including systemic lupus erythematosus, rheumatoid arthritis, progressive systemic sclerosis, ankylosing spondylitis, mixed connective tissue disease, Sjögren's syndrome, and various vasculitides; hypersensitivity lung disease or extrinsic allergic alveolitis; inorganic neumoconioses including silicosis, asbestosis, and berylliosis; drug-induced and iatrogenic entities; and disorders of unknown origin including sarcoidosis, idiopathic pulmonary fibrosis, eosinophilic granulomatosis, lymphangioleiomyomatosis, and bronchiolitis obliterans-organizing pneumonitis. Apart from these, there are many uncommon metabolic and immune disorders that can involve pulmonary interstitium. Recently developed epidemiologic, immunologic, and molecular biology techniques undoubtedly will add to the list other entities that may produce interstitial lung disease.