Pseudoachondroplastic Dysplasia
Pseudoachondroplasia is a rare genetic abnormal development of skeletal bones. It is a type of achondroplasia that is not apparent at birth, but becomes evident at about 2-3 weeks of age. Pseudoachondroplasia is different from achondroplasia in that it is characterized by short limbs and a normal head, while achondroplasia is characterised by short legs and enlarged head. The prefix "pseudo" before achondroplasia means that the disorder resembles achondroplasia but is actually different in that the signs are the same as for achondroplasia except the head is normal size. The disorder is caused by mutations in the cartilage oligomeric matrix protein (COMP) gene.
Signs & Diagnosis
The pseudoachondroplastic dogs are distinguished by a bone growth rate that is 65% of that in normal animals.4 Affected puppies show retarded growth and inability to walk or stand. The long bones are short, thick and bent, and the joints are enlarged and stiff. The flattened rib cage makes breathing difficult. General health is otherwise good except for arthritis. Both sexes may be affected. An autosomal recessive form of this disorder has been reported in Miniature poodles and Scottish deerhounds.
The diagnosis of pseudoachondroplasia can be made on the basis of clinical
findings and radiographic examination. Radiographically, the skull appears normal, but changes are present in the skeleton which are similar to those described in humans. In older animals, the bones are fully ossified but short and severely malformed.
References
- Roy Robinson. Genetics for Dog Breeders.
- GJ Breur, CE Farnum, GA Padgett and NJ Wilsman. Cellular basis of decreased rate of longitudinal growth of bone in pseudoachondroplastic dogs.
- Peter F. Jezyk. Constitutional Disorders Of the Skeleton In Dogs and Cats.
- C. G. Scanes. Biology of growth of domestic animals
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