Traditionally, “familial HLH” (FHL) has been defined as a genetic disease, in which the predisposition to HLH is the dominant feature (PERFORIN deficiency, MUNC13-4 deficiency, SYNTAXIN-11 deficiency, and MUNC18-2 deficiency) (12–17), while “immunodeficiencies with albinism” (Chediak–Higashi syndrome (CHS) or LYST deficiency, Griscelli syndrome type 2 (GS2) or RAB27A deficiency, and Hermansky–Pudlak syndrome type 2 (HPS2) or AP3b1 deficiency) (18–22) combine this predisposition with clinical manifestations of albinism and variable degrees of other immune cell and platelet dysfunction (23–28). This evidence concerns the gene AP3B1 and hyperinsulinemic hypoglycemia, familial, 4.