TAFAZZIN and Barth syndrome: For example, a rare hemizygous synonymous variant in TAZ: NM_000116.3:c.348C>T p.(Gly116Gly), a gene responsible for the mitochondrial membrane phospholipid and import machinery in which defects cause the X‐linked Barth syndrome, was shown to activate a cryptic donor sequence within exon 4, leading to the in‐frame deletion of eight amino acids (p.Lys117_Gly124del) within the tafazzin protein [74, 75].