Congenital myopathy – the role of pathogenic TNNT3 variants

Takeaway

  • This case report provides further evidence for the involvement of biallelic pathogenic TNNT3 variants in congenital myopathy, and the potential utility of TNNT3 sequencing and copy analysis in the work-up of patients with this condition.

Why this matters

  • TNNT3 is the gene that encodes fast skeletal muscle troponin T which has a major role in skeletal muscle contraction.

  • Pathogenic heterozygous variants in TNN3 were first found in families with autosomal dominant distal arthrogryposis type 2B2 (DA2B2) and involve a single arginine residue p.Arg63.

  • After a recent report of a neonate with nemaline myopathy, distal arthrogryposis and a homozygous TNNT3 splice variant (c.681 + 1G>1), this report describes a second patient with a new homozygous TNNT3 canonical splice site variant related to congenital myopathy.