Hagit Baris Feldman

1 INTRODUCTION Klippel–Feil syndrome (KFS) is a rare skeletal disorder which that 1:40,000 live births, with a slightly higher prevalence in females (60% of cases) (Frikha, 2020; Pizzutillo et al., 1994). The key clinical feature of KFS is a congenital fusion of at least two cervical vertebrae, which contributes to the typical triad observed in 50% of cases: an abnormally short neck, restricted movement of the head and neck, and a low hairline.

Abstract Intellectual disability encompasses a wide spectrum of neurodevelopmental disorders, with many linked genetic loci. However, the underlying molecular mechanism for more than 50% of the patients remains elusive. We describe pathogenic variants in SMARCA5, encoding the ATPase motor of the ISWI chromatin remodeler, as a cause of a previously unidentified neurodevelopmental disorder, identifying 12 individuals with de novo or dominantly segregating rare heterozygous variants.