In unclassified IBMFS, relevant genes include LIG4 (LIG4 syndrome: pancytopenia, severe immunodeficiency), ALDH2/ADH5 (AMeD syndrome: AA, intellectual disability, dwarfism), RECQL4 (Rothmund-Thomson syndrome: bilineage cytopenia), AP3B1 (Hermansky-Pudlak syndrome type 2: bone marrow failure), SRP72 (familial aplasia and myelodysplasia), and MYH9 (MYH9-related disorder: thrombocytopenia) [3, 5, 18, 23–25]. The gene discussed is AP3B1; the disease is immune system disorder.