Bi‐allelic NDUFC2 variants have not previously been reported in cases of mitochondrial disease; however, defects involving other ND2 module subunits have been associated with complex I deficiency (Fernandez‐Moreira et al, 2007; Berger et al, 2008; Hoefs et al, 2010; Minoia et al, 2017). Here, NDUFC2 is linked to hyperinsulinemic hypoglycemia, familial, 4.