These data obtained in dogs suggested that OF may contribute to tendon mechanics, as joint hypermobility and contractures found in patients with Marfan syndrome (MFS, OMIM 154700) and Beals syndrome (OMIM 121050), caused by mutations in the genes encoding fibrillin-1 and fibrillin-2, respectively (Urbán and Boyd, 2000; Gupta et al., 2002, 2004). This evidence concerns the gene FBN1 and congenital contractural arachnodactyly.