The six patients (P1, P2, P3, P4, P5 and P6) were clinically and/or biochemically diagnosed with galactosemia, mucopolysaccharidosis type I (MPS I), maple syrup urine disease (MSUD), hyperphenylalaninemia (HPA), citrullinemia and ornithine transcarbamylase (OTC) deficiency, respectively (Table 1). The gene discussed is OTC; the disease is classic galactosemia.