Given the observation that even apparently normal mucosa in patients with HPS is highly methylated [6], we investigated the potential for mutation or epigenetic disruption of DNMT1 (CCDS12228.1), DNMT3A (CCDS1718.1), DNMT3B (CCDS13204.1) and DNMT3L (CCDS13705.1) in the development of HPS. This evidence concerns the gene DNMT1 and Hermansky-Pudlak syndrome.