Recurrent variants were observed in five IMDs, including PAH gene variants c.728G>A, c.611A>G, and c.721C>T for phenylketonuria, PAH c.158G>A, c.721C>T, and c.728G>A for mild hyperphenylalaninemia, SLC22A5 c.1400C>G for primary carnitine deficiency, MMACHC c.609G>A, c.567dup and c.482G>A for methylmalonic acidemia, ACADS c.1055C>T, and c.1130C>T for short-chain acyl-CoA dehydrogenase deficiency, and ACADSB c.923G>A for 2-methylbutyrylglycinuria. The gene discussed is MMACHC; the disease is pulmonary arterial hypertension.