16 children (10%) with a known genetic abnormality (unrelated to GHD) were included in the SUS category (4 with muscular dystrophies; 3 with metabolic disorders such as Kearns-Seyre syndrome, GLUT1 deficiency, and hyperinsulinism/hyperammonemia syndrome; 4 with isolated genetic abnormalities such as Xp22.3 duplication, 13q21.2 deletion, 20q13.33 deletion and 2q37 deletion; 1 with tricho-entero-hepatic syndrome and 4 with syndromes known to affect growth such as ACAN mutation, Mazzanti syndrome and MIRAGE syndrome). The gene discussed is ACAN; the disease is hyperinsulinemic hypoglycemia, familial, 4.