A screening for coeliac disease was negative (IgA 142 mg/dl; tTG 0.2 U/mL), but an oral glucose tolerance test indicated hyperinsulinism (peak insulin level was 297 μU/mL), impaired glucose tolerance (120’ glycaemia 179 mg/dl), and marked insulin resistance (120’ insulin level 193 μU/mL). The gene discussed is CD79A; the disease is hyperinsulinism.