Canine Multiple System Degeneration (CMSD) Health Testing Guide

Canine Multiple System Degeneration (CMSD) is a hereditary neurological disorder affecting certain dog breeds, notably the Kerry Blue Terrier puppies and Chinese Crested puppies. This condition is characterised by progressive movement problems, typically appearing in young dogs around 3 months of age. CMSD is also sometimes called progressive neuronal abiotrophy (PNA), referring to the same disease.

CMSD manifests as movement abnormalities including changes in gait, head tremors, and loss of coordination. Although affected dogs typically remain cognitively aware, they gradually experience worsening difficulty walking which leads to a poor quality of life, often resulting in humane euthanasia before they reach two years of age.

Understanding Canine Multiple System Degeneration

This neurological disorder primarily affects puppies that initially appear healthy but start showing symptoms such as cerebellar ataxia—a loss of coordination and muscle control—between three to six months old. Early signs include involuntary shaking and nodding of the head, progressing to problems with balance and walking due to spinal and leg involvement.

Genetic Cause and Inheritance

CMSD is inherited as an autosomal recessive condition, meaning a puppy must inherit two faulty copies of the responsible gene—one from each parent—to be affected. Dogs are classified as clear (no faulty genes), carriers (one copy of the gene fault), or affected (two copies, showing symptoms).

Responsible breeding relies on understanding these genetic statuses to avoid mating two carriers or affected dogs. For example:

• Two clear dogs will produce a clear litter.
• Two carriers produce a mix: approximately 25% affected, 50% carriers, and 25% clear.
• One clear and one carrier produce litters of 50% carriers and 50% clear.
• Breeding an affected dog with a clear dog produces all carriers.

Health Testing for CMSD

The only accurate way to identify a dog's status is through DNA testing. Veterinarians can collect a blood sample or cheek swab, which is sent to specialised labs for genetic testing. This test indicates if the dog is clear, a carrier, or affected by CMSD.

This genetic screening is essential for breeders to make informed mating decisions, ultimately aiming to reduce and eliminate the condition within these breeds over time.

Practical Advice for Breeders and Buyers

Breeders of Kerry Blue Terriers or Chinese Crested dogs should ensure both parents are DNA tested before breeding and exclude affected dogs from breeding programmes. While breeding a carrier to a clear dog does not produce affected puppies, it does pass on the carrier status, so long-term planning is critical.

Prospective puppy buyers should choose reputable breeders who conduct health testing for CMSD and willingly share test results. Responsible buyers and breeders help promote healthier generations of these breeds.

Differentiating CMSD from Other Neurological Diseases

It is important not to confuse CMSD with degenerative myelopathy (DM), a separate neurodegenerative disease affecting mostly older dogs. CMSD arises in young puppies and progresses rapidly, while DM typically has an older onset and a different symptom pattern.

Supporting Your Dog’s Quality of Life

Currently, there is no cure or treatment that halts CMSD progression. Management focuses on comfort and quality of life. If your dog is diagnosed with CMSD, work closely with your vet to provide supportive care and consider all options with compassion.

Summary

Canine Multiple System Degeneration is a hereditary neurological condition impacting Kerry Blue Terriers and Chinese Crested dogs, presenting in puppies a few months old with progressive coordination and movement difficulties. Genetic health testing is the cornerstone of responsible breeding to prevent this disease. Buyers should prioritise health testing transparency from breeders. While no cure exists, supportive care remains vital for affected dogs.