The cupped metaphyses and cone-shaped epiphyses of knees with brachydactyly in patient 1 and 2 raised the possibility of acroscyphodysplasia (MIM:250215); however, this condition has recently been found to be associated with mutations in the GNAS locus16 and our patients did not have disease causing variants in the GNAS gene, nor in the genes responsible for the other above mentioned differential diagnoses. This evidence concerns the gene GNAS and brachydactyly.