Allelic series include those conditions caused by mutations in the genes encoding type II collagen (COL2A1), cartilage oligomeric matrix protein (COMP), fibroblast growth factor receptor 3 (FGFR3) and the diastrophic dysplasia sulfate transporter (DTDST).
Multipoint linkage analysis gave a lod score of -2.95, which conclusively excluded the COL2A1 gene as the mutation site in diastrophic dysplasia in these families.