Individuals carrying single mutated copies of Collagen 10 alpha-1, (COL10A1) suffer from Metaphyseal chondrodysplasia, Schmid type, (MCDS), involving mild to moderate short stature and skeletal deformities of the limbs. We describe individuals with two mutated copies of COL10A1, exhibiting extreme short stature and severe lower limb deformities. However, individuals with single mutated copies had below average heights and no apparent skeletal defects. This mutation was located in the NC2 domain, in which no pathogenic variants have been described before. This is the first report of a COL10A1 variant with autosomal recessive skeletal dysplasia and suggests that some COL10A1 alleles may be involved in isolated short stature. (By Dr. Sadaf Naz, http://jmg.bmj.com/content/early/2017/08/22/jmedgenet-2017-104885 )