These abnormalities include complete hypoxanthine-guanine phosphoribosyl transferase (HGPRT) deficiency (Lesch–Nyhan syndrome), partial HGPRT deficiency (Kelly–Seegmiller syndrome), adenine phosphoribosyl transferase (APRT) deficiency, phosphoribosyl pyrophosphate (PRPP) synthetase overactivity, and myoadenylate deaminase deficiency. This evidence concerns the gene HPRT1 and hyperinsulinemic hypoglycemia, familial, 4.