SERPINH1 and idiopathic pulmonary fibrosis: Although a precise mechanism for the above unexpected observation was not elucidated in this study, the following is hypothesized: 1) We recently reported that HSP47 expression was higher in DAD lung that resulted in a final diagnosis of acute exacerbation of IPF than in UIP lungs, and that HSP47 serum levels in patients with acute exacerbation of IPF were found to be markedly higher than in patients with stable IPF[23].