These cases included 4 cases of amino acid metabolic disease (50.00%): 2 cases of PKU, 1 case of citrin deficiency and 1 case of tyrosinemia type I (HT-1); 2 cases of organic acid metabolic disease (25.00%):1 case each of methylmalonic acidemia (MMA) and glutaric aciduria type I (GA-I); 2 cases (25.00%) of fatty acid oxidation disorders: 1 case each of carnitine palmitoyltransferase II (CPT II) deficiency and primary carnitine deficiency (PCD) (Table 2). The gene discussed is CPT2; the disease is hematocrit.