Canine Degenerative Myelopathy and Genetic Testing in Pembroke Welsh Corgis By Jerold S Bell DVM Degenerative myelopathy (DM) is a specific genetic disease causing spinal cord degeneration in older dogs. It has a complex mode of inheritance with the effect of more than one gene pair having to combine to cause a clinically affected dog. Affected dogs begin to show signs of the disorder usually between 8 and 14 years of age. The average age of onset in Pembroke Welsh Corgis is 11 years of age. Sporadic cases of clinically affected dogs have been pathologically confirmed in 34 pure-breeds and in mixed breed dogs, but the majority of clinical cases occur in only a handful of breeds including the Pembroke Welsh Corgi. The clinical signs of DM begin with; weakness of the hind legs, scuffing of the hind toes, crossing of the hind legs, and progressing to dragging of the hind legs. The progression is slow, occurring over 6 months to 2 years. With excellent nursing care (and a …