The previously reported c.809C > T (p.T270M) variant in the BLK gene was found in a 13-year-old overweight male patient with autoantibody-negative hyperglycemia and a strong family history of diabetes, which includes his mother, maternal grandfather, all 5 sisters of his grandfather, and 2 cousins of his mother. The gene discussed is BLK; the disease is Hyperglycemia.