In humans, genomic mutations in the GDF5 gene result in various chondrogenic dysplasias, while polymorphisms in the gene are associated with osteoarthritis.139, 140, 141, 142 Similarly, mutations at the GDF6 gene locus on chromosome 8 are known to cause both familial and sporadic cases of Klippel‐Feil syndrome (KFS) leading to similar carpal, tarsal and vertebral fusions as seen in mice GDF5/6 knockouts.23 The incomplete nature of these carpal and tarsal fusions in GDF6 knockout mice and in some familial cases of KFS in humans indicates a degree of redundancy in GDF signaling. This evidence concerns the gene PAEP and Klippel-Feil syndrome 1, autosomal dominant.