NGS revealed a homozygous FKTN variant in the index case (p.Gly424Ser, rs752358445), classified as likely pathogenic by ACMG criteria. Both parents and an unaffected brother were heterozygous carriers. Since the siblings had no apparent skeletal muscle weakness or central nervous system involvement, FKTN mutations were not initially suspected.
Conclusions:
This is the first report demonstrating that heterozygous individuals for the FKTN p.Gly424Ser mutation were healthy, while two homozygous brothers suffered severe DCM, strongly suggesting that this FKTN mutation is a rare cause of autosomal recessive DCM.