Diagnoses were incorrect in some of the cases reviewed for the following IEM: carbamylphosphate synthase I deficiency (two out of four reviews), ornithine transcarbamylase deficiency (1/4), homocystinuria (1/6), tyrosinemia type I (1/4), carnitine transporter deficiency (1/2) and 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency (1/2). Here, OTC is linked to homocystinuria.