Genetic basis - GCL, or Krabbe’s Disease, is caused by mutations in the GALC (galactocerebrosidase) gene, which encodes a lysosomal enzyme critical for myelin maintenance in the nervous system. Various breed-specific mutations have been identified: West Highland White and Cairn Terriers carry a c.473A>C mutation (tyrosine to serine substitution). Irish Setters have a 78 base pair insertion mutation (c.790_791ins) causing an inactive enzyme. Novel variants have been identified in mixed-breed dogs as well. The disease is inherited in an autosomal recessive manner, requiring two copies of the mutant GALC gene to develop clinical disease.
Pathophysiology - Deficiency of GALC enzyme causes accumulation of galactocerebroside metabolites and psychosine, a toxic metabolite that leads to oligodendrocyte death and demyelination of nerve fibers. Demyelination causes progressive neurological decline due to impaired nerve signal transmission.
Complications - Clinical signs appear between 1 to 6 months of age, varying by breed and mutation. Symptoms include muscle tremors, ataxia, progressive weakness, loss of coordination, vision loss, and seizures. Disease progression is rapid and ultimately fatal, with euthanasia often necessary by 1 year of age. Associated signs include dementia, incontinence, failure to thrive, and behavioral changes.
Why This Matters to Breeders and Vets - For breeders, prevention of GCL through genetic testing preserves breed health and prevents breeding affected dogs with fatal neurological disease. Veterinarians use knowledge of the disease for early diagnosis, counseling owners, and management of clinical signs. Understanding genetics helps in better advising breeders and owners about risks, care, and reproductive decisions. Reducing the mutation frequency preserves overall breed vigor and welfare.