SLC25A13 and phenylketonuria: The total incidence of amino acid metabolic diseases was 1/13,998, of which there were six cases of phenylalanine hydroxylase deficiency (PHD) (1/18,664; highest), one case of hyperhomocysteinemia (1/111,986), and one case of citrullinemia type l (CTLN2; 1/111,986).