Defects in RAB27A, LYST, and AP3B1, leading to Griscelli syndrome type 2 (GS2), Chediak-Higashi syndrome (CHS), and Hermansky-Pudlak syndrome type 2 (HPS2), respectively, also cause defective degranulation. The gene discussed is AP3B1; the disease is Chédiak-Higashi syndrome.