Instability of BLOC-2 and BLOC-3 in Chinese patients with Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) is a rare recessive disorder characterized by oculocutaneous albinism (OCA) or ocular albinism (OA), bleeding tendency, and other symptoms due to multiple defects in tissue-specific lysosome-related organelles. Ten HPS subtypes have been characterized with mutations in HPS1 to HPS10, which encode the subunits of BLOC-1, -2, -3, and AP-3. Using next-generation sequencing (NGS), we have screened 100 hypopigmentation genes in OCA or OA patients and identified four HPS-1, one HPS-3, one HPS-4, one HPS-5, and three HPS-6. The HPS-4 case is the first report in the Chinese population. Among these 20 mutational alleles, 16 were previously unreported alleles (6 in HPS1, 1 in HPS3, 2 in HPS4, 2 in HPS5, and 5 in HPS6). BLOC-2 and BLOC-3 were destabilized due to the mutation of these HPS genes which are so far the only reported causative genes in Chinese HPS patients, in which HPS-1 and HPS-6 are the most common subtypes. The mutational spectrum of Chinese HPS is population specific.