Historically, 3‐methylglutaconyl‐CoA hydratase deficiency (OMIM no. 250950; also known as 3‐methylglutaconic aciduria Type 1 [MGA1]) was thought to be a benign biochemical abnormality, given many patients had normal development in childhood.1, 6. Here, CUBN is linked to hyperinsulinemic hypoglycemia, familial, 4.