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Phenotypic Evolution in a Boy with MYL11-Related Distal Arthrogryposis Type 1C: A Case Report
Rajesh K Maurya1, Niladri Das1, Shubha R Phadke1
1Department of Medical Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
Introduction:
Distal arthrogryposis (DA) type 1C (DA1C) is characterized by multiple congenital contractures, scoliosis, and short stature. It is caused by biallelic variants in MYL11(MYLPF), which encodes a regulatory myosin light chain in fast-twitch skeletal muscle.
Case Presentation:
We evaluated a 3-year-old boy from a consanguineous family presenting with features of distal arthrogryposis. Clinical, radiographic, and electrophysiological assessments were performed. He had distal joint contractures, camptodactyly, cutaneous syndactyly of the second and third toes, absent distal interphalangeal creases, left-sided inguinal hernia, facial dysmorphism, and short stature. Exome sequencing failed to detect any candidate variants. On re-analysis after 7 years, we identified a homozygous NC_000016.10:g.30377860G>T; MYL11(NM_013292.5):c.470G>T; p.(Cys157Phe) variant, which causes DA1C. This variant was reported by Chong et al. in 2020 in seven patients with MYL11-related disorders and was classified as pathogenic.
Conclusions:
This study extends the spectrum of MYL11-related disorders by identifying a phenotype of distal arthrogryposis with marked facial dysmorphism reminiscent of DA2, along with other findings like absent distal interphalangeal joint creases, hirsutism, inguinal hernia, and syndactyly of the 2nd and 3rd toes. This report also highlights the critical role of periodic re-analysis of previously uninformative exome cases.
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