SERAC1 deficiency is one of the signature disorders of an emerging and rapidly growing new class of disorders affecting the biosynthesis and remodeling of complex lipids.5, 6 So far, 2 further genetic syndromes have been linked to the cardiolipin biosynthetic pathway: AGK deficiency (Sengers syndrome, consisting of 3‐methylglutaconic aciduria [3‐MGA‐uria], cardiomyopathy, and cataracts, MIM #212350) and TAZ deficiency (Barth syndrome, consisting of 3‐MGA‐uria, cardiomyopathy, and neutropenia, MIM #302060). The gene discussed is AGK; the disease is Sengers syndrome.