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. Here, DNMT3B is linked to Hermansky-Pudlak syndrome.