FGF4 and intervertebral disk degenerative disorder: An FGF4 retrogene on CFA18, 25 Mb from the parental gene, associated with marked limb length variation (14), and an FGF4 retrogene on CFA12 associated with chondrodystrophy characterized by moderate variation in limb length and an odds ratio of 51.23 (95% CI = 46.69, 56.20) for Hansen Type I intervertebral disc disease (13).