Several recurrent variants were observed among 5 IMD types, including PAH gene variants c.728G>A, c.611A>G, and c.721C>T in phenylketonuria; PAH gene variants c.158G>A, c.721C>T, and c.728G>A in mild hyperphenylalaninemia; SLC22A5 gene variant c.1400C>Gin PCD; MMACHC gene variants c.609G>A, c.567dup, and c.482G>A in MMA; ACADS gene variants c.1055C>T and c.1130C>Tin short-chain acyl-CoA dehydrogenase deficiency (SCADD); and ACADSB gene variant c.923G>A in 2-methylbutyryl-CoA dehydrogenase deficiency (SBCADD). The gene discussed is MMACHC; the disease is pulmonary arterial hypertension.