Idiopathic pulmonary fibrosis: is it a familial disease?

Idiopathic pulmonary fibrosis is a progressively fatal interstitial lung disease associated with pathological findings of usual interstitial pneumonia. Its pathogenesis is unknown, and there are no proven effective therapies. Familial cases account for 0.5-2% of idiopathic pulmonary fibrosis. Familial idiopathic pulmonary fibrosis occurs as an autosomal dominant disorder with variable penetrance. The clinical characteristics of familial idiopathic pulmonary fibrosis are indistinguishable from sporadic idiopathic pulmonary fibrosis. These marked similarities support the hypothesis there may, in part, be a genetic basis for idiopathic pulmonary fibrosis.

Many investigations have evaluated genetic polymorphisms and idiopathic pulmonary fibrosis. Candidate genes include cytokines and surfactant protein genes. To date, no gene has been consistently identified to be associated with idiopathic pulmonary fibrosis. Recent studies in familial idiopathic pulmonary fibrosis have demonstrated a strong association with surfactant protein C gene mutations in one large kindred.

The pathogenesis of both idiopathic pulmonary fibrosis and familial idiopathic pulmonary fibrosis remains unclear. A consistent genetic basis has not yet been demonstrated in all cases. Other factors, including variable gene expression, co-carriage of other modifying genes and environmental stimuli, particularly cigarette smoke, significantly contribute to disease expression.