Compound heterozygous mutation of MUSK causing fetal akinesia deformation sequence syndrome: A case report

Background: Fetal akinesia deformation sequence (FADS) is a broad spectrum disorder with absent fetal movements as the unifying feature. The etiology of FADS is heterogeneous and mostly still unknown. A prenatal diagnosis of FADS relies on clinical features obtained by ultrasound and fetal muscle pathology. However, the recent advances of next-generation sequencing (NGS) can effectively provide a definitive molecular diagnosis.

Case summary: A fetus presented after 24 wk and 6 d of gestation with absent fetal movements and multiple abnormal ultrasonographic signs. The mother had had a previous abortion due to a similarly affected fetus a year before. A clinical diagnosis of FADS was made. The parents refused cord blood examination and chose abortion. A molecular diagnosis of fetal muscle using NGS of genes found a compound heterozygous mutation in the MUSK gene: c.220C > T (chr9: 113449410 p.R74W) and c.421delC (chr9: 113457745 p.P141fs).

Conclusion: To our knowledge, this is the first report in China showing that a mutation in MUSK is associated with FADS. This supports previous finding that a lethal mutation of MUSK will cause FADS. A precise molecular diagnosis for genetic counseling and options for a prenatal diagnosis of FADS are very important, especially for recurrent FADS; this may also provide evidence for both prenatal and preimplantation genetic diagnoses.