This is in contrast with the latest International Union of Immunological Societies (IUIS) classification of the inborn errors of immunity, where ARPC1B deficiency is classified as a combined immune deficiency with congenital thrombocytopenia, along with the Wiskott–Aldrich syndrome protein-interacting protein (WIP) deficiency (1). The gene discussed is ARPC1B; the disease is hyperinsulinemic hypoglycemia, familial, 4.