Previously 3‐methylglutaconic aciduria (3‐MGA) had been reported in many cases of neonatal‐onset CPS1 deficiency,3, 4 as well as patients with ornithine transcarbamylase (OTC) deficiency and argininosuccinate lyase (ASL) deficiency,5 but not in NAGS deficiency.4 The gene discussed is CPS1; the disease is hyperinsulinemic hypoglycemia, familial, 4.