Our data indicate that biallelic loss-of-function mutations in CSGALNACT1 disturb glycosaminoglycan synthesis and cause a mild skeletal dysplasia with advanced bone age, CSGALNACT1-CDG.
We here identify a second case and the first juvenile patient with a homozygous frameshift variant in CSGALNACT1 which corroborates its role in mild and non-progressive skeletal dysplasia with joint laxity.
This is the first description of bi-allelic loss-of-function mutations in CSGALNACT1 that produce a skeletal dysplasia reminiscent of the skeletal dysplasia of Csgalnact1<sup>-/-</sup> mice, and adds to the genetic heterogeneity of DD.