By age 12, he presented with short stature (146.2 cm, −2.1 SD), poor appetite, delayed puberty, and hyperglycemia (fasting 5.96 mmol/L; postprandial 17–18 mmol/L) with low C-peptide (0.172 ng/ml), consistent with type 1 diabetes mellitus; insulin therapy was initiated, but frequent hypoglycemic episodes ensued. The gene discussed is INS; the disease is type 1 diabetes mellitus.