OCA can be caused by TYR, TYRP1 or MATP gene mutation; GS may be caused by pathogenic variants in MYO5A, RAB27A or MLPH; at least nine subtypes of hermansky-pudlak syndrome (HPS), HPS2 caused by variants in AP3B1 which most closely resembles CHS. The gene discussed is LYST; the disease is Gerstmann syndrome.