Our study showed that HPS2-mice had elevated transcript levels of MMP2 and MMP9, while broad upregulation of MMP2, -3, -8, -9, -12, and -14 transcripts was evidenced in the HPS1-mice, suggesting that the pathogenesis of pulmonary fibrosis might differ in the different HPS mutations. This evidence concerns the gene MMP9 and pulmonary fibrosis.