ELAC2 and hyperinsulinemic hypoglycemia, familial, 4: Proband 3-II-3 suffered from infantile-onset HCM and carried a pathogenic variant (p.Phe154Leu) in ELAC2. Previously, the patients harboring this variant experienced lactic acidosis, mitochondrial complex I deficiency, and, similarly, an infantile-onset HCM23,24.