Globoid Cell Leukodystrophy in a Litter of Kelpies with Episodic Cerebellar Disease
Globoid cell leukodystrophy (GLD) is a rare, autosomal recessive lysosomal storage disease that results in progressive degeneration of white matter of the CNS and PNS in several dog breeds. The disease is caused by mutations in the gene encoding for the lysosomal enzyme galactosylceramidase (GALC), which results in an accumulation of psychosine (galactosylsphingosine), which is highly toxic to oligodendrocytes and Schwann cells. The genetic mutation for GLD has been identified in West Highland White terriers, Cairn terriers and Irish Setters. The clinical signs associated with this disease are variable and may reflect a multifocal syndrome, often presenting as ascending pelvic limb paresis, lower motor neuron signs, cerebellar signs or (partial) seizure activity. Episodic cerebellar signs have not been reported with this disorder in dogs. We report the presentation and diagnosis of GLD in Kelpies.
Three affected dogs (one female and two males) from a litter of eight were all presented at the age of 14 months with a nine to eleven-month history of episodic paroxysmal events. Video footage of the events depicted cerebellar ataxia of the head, trunk and limbs, hypermetria and hypertonia of the pelvic limbs, and intermittent decerebellate rigidity. They occurred about every three weeks and were of five minutes duration on average. In between the episodes the dogs were neurologically normal. The frequency and severity of these events were non-progressive after 12 months from diagnosis. Hematology and serum biochemistry, MRI of the brain, CSF analysis (including PCR for Canine distemper virus, Toxoplasma gondii, and Neospora caninum), electrodiagnostic testing and pelvic limb muscle biopsies were unremarkable. A skin biopsy was taken for fibroblast culturing from all three dogs. In two patients there was no detectable activity of GALC, and GALC activity was reduced in the remaining dog by more than 50% compared to healthy controls. The parents and siblings were reported to be clinically unaffected. Investigations to identify the genetic mutation leading to this untypical presentation of GLD in Kelpies are currently underway.