Histologically, the lungs in IPF demonstrate a usual interstitial pneumonia (UIP) pattern of injury, a pattern characterized by several pertinent findings: geographically heterogenous areas of dense fibrosis, interspersed areas of relatively normal-appearing lung architecture, small cysts lined by ciliated respiratory epithelium and often filled with mucin (i.e., honeycombing), and juxtaposed areas of extracellular matrix with spindle-shaped fibroblasts (i.e., fibroblast foci) [1,2,3,5,6]. The gene discussed is MUC5AC; the disease is idiopathic pulmonary fibrosis.