• Idiopathic Pulmonary Fibrosis
• Sarcoidosis
• Systemic Disease and Lungs

Idiopathic pulmonary fibrosis (IPF), sarcoidosis and systemic sclerosis can each cause diffuse parenchymal lung disease involving alveolar epithelial abnormalities, and manifest as interstitial lung fibrosis. Systemic sclerosis is an autoimmune connective tissue disease and sarcoidosis is a multisystem granulomatous disease; the development of lung fibrosis in both conditions generally indicates a poor prognosis. IPF is a progressive disease which is thought to occur after recurrent injury to the alveolar epithelium followed by dysregulation of cellular homoeostasis, abnormal repair and excessive deposition of extracellular matrix, ultimately leading to loss of lung function.1 Mortality 3–5 years after diagnosis of IPF is 50%, and treatment options are currently limited.

Seibold et al2 have previously shown that a variant single-nucleotide polymorphism (SNP) in the promoter region of an airway mucin gene (MUC5B) is associated with greatly increased production of MUC5B, and with pulmonary fibrosis. This suggested that dysregulated MUC5B expression in the lung may be key to the pathogenesis of pulmonary fibrosis. One hypothesis is that an excess of MUC5B causes bronchiolar plugging and impairs mucosal host defence, reducing clearance …