TMEM70 and hyperinsulinemic hypoglycemia, familial, 4: Transmembrane protein 70 (TMEM70) deficiency (TMEM70, autosomal recessive, MIM #614052) is the most frequently reported cause of nuclear‐encoded ATP synthase deficiency, resulting in a neonatal encephalocardiomyopathy with lactic acidosis and hyperammonaemia.102