Introduction Arthrogryposis is characterized by the presence of multiple contractures at birth and can be caused by pathogenic variants in TTN (Titin). Exons and variants that are not expressed in one of the three major isoforms of titin are referred to as “metatranscript-only” and have been considered to be only expressed during fetal development. Recently, the metatranscript-only variant (c.39974–11T > G) in TTN with a second truncating TTN variant has been linked to arthrogryposis multiplex congenita and myopathy.

Methods Via exome sequencing we identified the TTN c.39974–11T > G splice variant in trans with one of three truncating variants (p.Arg8922*, p.Lys32998Asnfs*63, p.Tyr10345*) in five individuals from three families. Clinical presentation and muscle ultrasound as well as MRI images were analyzed.

Results All five patients presented with generalized muscular hypotonia, reduced muscle bulk, and congenital contractures most prominently affecting the upper limbs and distal joints. Muscular hypotonia persisted and contractures improved over time. One individual, the recipient twin in the setting of twin-to-twin transfusion syndrome, died from severe cardiac hypertrophy 1 day after birth. Ultrasound and MRI imaging studies revealed a recognizable pattern of muscle involvement with striking fibrofatty involvement of the hamstrings and calves, and relative sparing of the femoral adductors and anterior segment of the thighs.

Conclusion The recurrent TTN c.39974–11T > G variant consistently causes congenital arthrogryposis and persisting myopathy providing evidence that the metatranscript-only 213 to 217 exons impact muscle elasticity during early development and beyond. There is a recognizable pattern of muscle involvement, which is distinct from other myopathies and provides valuable clues for diagnostic work-up.

The principal author and the senior author take full responsibility for the data, analyses, and interpretation, and the conduct of the research; they have full access to all of the data; and that they have the right to publish any and all data, separate and apart from the guidance of any sponsor.

Data is not provided in the article because of space limitations but may be shared (anonymized) at the request of any qualified investigator for the purpose of replicating procedures and results.

L.A., F.D., and S.D. contributed toward conceptualization. L.A., S.D., D.H., S.W., S.S., U.L., A.S.J., T.H., D.G., A.R., K.R.C., and S.B.N. contributed toward data acquisition. L.A., S.W., and S.S. did the illustrations. F.D., E.M., and C.G.B. reviewed the manuscript. L.A. and F.D. drafted the manuscript.

Received: 07 January 2022

Accepted: 18 May 2022

Accepted Manuscript online:
23 May 2022

Article published online:
02 October 2022

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