We previously reported that this patient was diagnosed with PGK-1 deficiency at 3 years of age based on decreased PGK activity in erythrocytes (16 IU/g Hb, normal: 255–325 IU/g Hb) and the novel PGK-1 missense mutation c.1060G > C; p.A354P.4 (Notably, this mutation was originally described as A353P, which indicates an amino-acid substitution at the 353rd position from the NH2-terminal serine residue.4). The gene discussed is PGK1; the disease is hyperinsulinemic hypoglycemia, familial, 4.