Genetic basis of CMSD - is an early onset, progressive movement disorder affecting Kerry Blue Terriers and Chinese Crested dogs. In Kerry Blue Terriers, CMSD is caused by a nonsense mutation in exon 15 of the SERAC1 gene, located on canine chromosome 1. The disease is inherited in an autosomal recessive manner, meaning affected dogs have two copies of the mutated gene, while carriers have one copy and appear normal but can pass the mutation on. This mutation leads to a loss of function in the SERAC1 protein, which is important for mitochondrial function and lipid remodeling.
Pathophysiology - The mutation causes degeneration of neurons in critical brain regions including the cerebellum, substantia nigra, putamen, and caudate nucleus. This leads to progressive movement abnormalities similar to those seen in juvenile Parkinson's disease in humans. Neuronal loss includes Purkinje cells in the cerebellum and other brain areas responsible for motor control. Affected dogs develop cerebellar ataxia, tremors, postural instability, and gait abnormalities that worsen over time.
Complications - Symptoms typically appear between 3 to 6 months of age with cranial intention tremors (head shaking especially when focused) and cerebellar ataxia. Early signs include a goose-stepping gait and occasional falls. By 6 to 8 months, signs worsen with more frequent falls, festination gait (rapid small steps), dysmetria (incoordination), severe postural instability, and akinesia (loss of voluntary movement). Most affected dogs become incapacitated by 12 to 18 months and are typically euthanized due to severe disability. Magnetic resonance imaging shows cerebellar atrophy.
Why This Matters to Breeders and Vets - Knowledge of this genetic mutation allows breeders to identify carriers through DNA testing and avoid mating two carriers to prevent affected puppies. Early diagnosis by veterinarians helps differentiate CMSD from other movement disorders and guides prognosis and management. Understanding the progressive nature of CMSD is essential for providing appropriate care and owner counseling. Genetic screening is a valuable tool to maintain breed health while preserving genetic diversity.
Summary - Canine Multiple System Degeneration (CMSD) in Kerry Blue Terriers is a fatal autosomal recessive neurological disorder caused by a nonsense mutation in the SERAC1 gene. It leads to early-onset cerebellar ataxia, tremors, and progressive movement disorders resembling juvenile Parkinson’s disease, resulting in severe disability and euthanasia by 12 to 18 months of age. Genetic testing enables carrier identification and informed breeding decisions to reduce disease incidence while maintaining the breed's genetic health.