Although previous studies have described increased AT2 cell apoptosis in HPS1/2 mice as well as in bleomycin-challenged but not naive HPS1 and HPS2 single-mutant mice, we did not detect AT2 cell apoptosis in any of the HPS models up to 48 weeks of age (8, 10). Here, HPS1 is linked to Hermansky-Pudlak syndrome.