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Osteochondrodysplasia and Achondroplasia in Dogs

Osteochondrodysplasia (OCD) is a growth and developmental abnormality of the bone and cartilage, which results in lack of normal bone growth and bone deformities. Where osteo refers to the bone, chondro refers to the cartilage, and dysplasia is a general term that is applied to abnormal growth. Dog breeds that tend to be predisposed to this disorder are great Pyrenees, Alaskan malamutes, Samoyeds, Scottish deerhounds, Labrador retrievers, basset hounds, and Norwegian elkhounds.

Achondroplasia is a form of osteochondrodysplasia in which the bones do not grow to the normal size, based on what is expected of the breed. This is caused by a mutation of the fibroblast growth factor receptor gene. The result is abnormally short limbs, a condition called dwarfism. In some breeds this trait is selectively encouraged, such as with the dachshund, Skye terrier, and Welsh corgi. Other breeds that are reported to be affected are bulldogs, German shepherds, basset hounds, Boston terriers, pugs, Pekingese, Japanese spaniels, shih-tzus, beagles, English pointers, cocker Spaniels, and Scottish terriers.

These disorders are genetically acquired.

Symptoms and Types

• Larger than normal head
• Undershot jaw with shorter nose
• Crooked teeth due to shorter jaw
• Abnormal bone shape
• Poor growth or lack of growth
• Bones appear shorter than normal
• Enlarged joints
• Sideways bowing of forelimbs – front legs are more likely affected
• Spinal deviation to either side of the body

Causes

Osteochondrodysplasia is an autosomal dominant genetic disorder, meaning that it can be passed along by either gender and only one parent need carry the gene for an offspring to be potentially affected.

Diagnosis

You will need to give your veterinarian a detailed medical history, including when you first noticed symptoms of growth abnormality, and any information you have about your dog's genetic background. Routine laboratory testing will include a complete blood count, biochemistry profile and urinalysis to rule out other causes for the disorder. X-rays of the affected limbs will be taken, which will show abnormalities related to bone growth and structure. X-rays of the spine will also show such abnormalities in patients with spinal deviation. To confirm a diagnosis, your veterinarian will take a sample of tissue from the small bones of the body and send it to a veterinary pathologist for further diagnostic testing.