Description:  One of the most striking differences between dog breeds is the different lengths of the limbs and in some breeds extremely short limbs. This morphological feature is the result of abnormal growth of developing limbs due to defects in the process of endochondral ossification. Short limbs were associated with two conditions: chondrodysplasia and chondrodystrophy. Chondrodysplasia (CDPA) is defined as an inherited condition characterized by abnormal growth at the ends of bones, particularly the long bones. In dogs, CDPA was associated with FGF4 gene insertion on chromosome 18, which is inherited as an autosomal dominant trait and found to cause short-legged phenotype in Basset Hound, Welsh Corgi, Dachshund, West Highland White Terrier, and Scottish Terrier. Chondrodystrophy (CDDY) in dogs is defined by dysplastic, shortened long bone, premature cartilage degeneration, and calcification, resulting in degeneration of type I intervertebral discs (IVDD). Abnormal discs are predisposed to herniation leading to IVDD in dogs at a young age.  CDDY/IVDD was associated with FGF4 gene insertion on chromosome 12, which is inherited in semi-dominant manner in respect to height (dogs with 2 copies of the mutation have shorter legs than dogs with one copy of the mutation) and dominant for IVDD (dogs with one or two copies of the mutation are at risk for IVDD). It affects multiple breeds, including: English Cocker Spaniel, Jack Russell Terrier, French Bulldog, Chihuahua, Shih Tzu, Bichon and more. This mutation was found in many dog breeds. The manifestation of IVDD (Intervertebral disc disease) has an autosomal dominant inheritance.

Inheritance: IVDD autosomal dominant, Truncation of the limbs has semidominant inheritance

Mutation: insertion of retrogene FGF4 to CFA18 and CFA12 (CFA-canine chromosome)

Sample: EDTA whole blood (1.0 ml) or 2 buccal brushes. For official purposes, the confirmation of the dog’s identity by Veterinarian is recommended.

The analysis is suitable for the following breeds: American Cocker Spaniel, Beagle, Cocker Spaniel, Coton de Tulear, Dachshunds, French Bulldog, Nova Scotia Duck Tolling Retriever, Pekingese, Shih Tzu, Welsh Corgi, and more

Notes: Chondrodysplasia is not an unwanted condition for dogs with normally short legs. In this case, short legs are their characteristic trait. Tests for the detection of these mutations can help breeders to determine whether CDDY (chondrodystrophy) is present in breeding animals and thus identify dogs predisposed to IVDD (intervertebral disc degeneration). For breeds with both mutations, the results will then help in the implementation of breeding strategies to reduce the occurrence of the mutation for CDDY while maintaining the desired short leg phenotype.