TAFAZZIN and hyperinsulinemic hypoglycemia, familial, 4: Mutations in the TAZ result in CL deficiency, and increase the monolysocardiolipin (MLCL) to cardiolipin ratio (MLCL/CL) accompanied by structural and functional defects in mitochondria of affected individuals and Taz knockdown (TazKD) mice [1, 2].