A hypomyelinating leukodystrophy in German Shepherd dogs

Congenital spongiform leukodystrophy in 2 female littermate German shepherd puppies

Two 9-week-old female littermate German Shepherd puppies showed severe high-frequency low-amplitude trembling that worsened with movement. The white matter (WM) of the central nervous system (CNS) showed bilateral diffuse severe spongiosis in the cerebellum, brainstem, spinal cord, and the neuropil of the oculomotor and red nuclei. The cortical corona radiata was less severely affected. Rare necrotic or apoptotic glia-like cells also were identified in the WM. Luxol fast blue staining disclosed severe diffuse myelin loss in the entire CNS; peripheral nerves were spared. Glial fibrillary acidic protein immunohistochemistry showed diffuse astrogliosis and astrocytosis in the WM. Genetic analyses of the littermates excluded the aspartoacylase (ASPA) gene as a candidate for this condition in dogs. In conclusion, this description of a rare congenital spongiform leukodystrophy in the German Shepherd breed, closely resembling to Canavan disease in humans, is likely caused by a genetic alteration unrelated to the ASPA gene.

Canine models of Charcot-Marie-Tooth: MTMR2, MPZ, and SH3TC2 variants in golden retrievers with congenital hypomyelinating polyneuropathy

Congenital hypomyelinating polyneuropathy (HPN) restricted to the peripheral nervous system was reported in 1989 in two Golden Retriever (GR) littermates. Recently, four additional cases of congenital HPN in young, unrelated GRs were diagnosed via neurological examination, electrodiagnostic evaluation, and peripheral nerve pathology. Whole-genome sequencing was performed on all four GRs, and variants from each dog were compared to variants found across >1,000 other dogs, all presumably unaffected with HPN. Likely causative variants were identified for each HPN-affected GR. Two cases shared a homozygous splice donor site variant in MTMR2, with a stop codon introduced within six codons following the inclusion of the intron. One case had a heterozygous MPZ isoleucine to threonine substitution. The last case had a homozygous SH3TC2 nonsense variant predicted to truncate approximately one-half of the protein. Haplotype analysis using 524 GR established the novelty of the identified variants. Each variant occurs within genes that are associated with the human Charcot-Marie-Tooth (CMT) group of heterogeneous diseases, affecting the peripheral nervous system. Testing a large GR population (n = >200) did not identify any dogs with these variants. Although these variants are rare within the general GR population, breeders should be cautious to avoid propagating these alleles.

Diagnostic features of type II fibrinoid leukodystrophy (Alexander disease) in a juvenile Beagle dog

A 3-month-old female entire Beagle presented with a progressive history of caudotentorial encephalopathy. Reactive encephalopathies were ruled out and tests for the most common infectious diseases agents were negative. Magnetic resonance imaging of the brain using a 1.5 Tesla scanner showed diffuse, bilateral, T2-weighted and T2-weighted-FLAIR hyperintense, T1-weighted hypointense, noncontrast-enhancing lesions involving the white matter of the cerebellum, brainstem, spinal cord, and forebrain to a lesser extent. There was cerebellar enlargement. Abnormalities were not detected on cerebrospinal fluid examination. Given the progressive nature of the disease and suspected poor prognosis the dog was euthanized. Histopathological analysis of the brain was consistent with fibrinoid leukodystrophy, also known as Alexander disease. Based on the classification used in humans, this is a description of MRI of a case of type II Alexander disease in veterinary medicine, with characteristics different to other described leukoencephalopathies in dogs.

Case Report: MRI, Clinical, and Pathological Correlates of Bromethalin Toxicosis in Three Dogs

Bromethalin toxicosis is an increasingly common clinical presentation in dogs that may be fatal depending on the extent of intoxication. Antemortem diagnosis of bromethalin toxicosis was achieved in three dogs by demonstration of the active metabolite desmethylbromethalin in fat or serum. Magnetic resonance imaging (MRI) findings were consistent with a diffuse leukoencephalopathy with restricted diffusion and prominent involvement of the corticospinal motor tracts on T2-weighted and diffusion-weighted sequences. Imaging findings were confirmed in one non-surviving dog at necropsy. Resolution of MRI abnormalities was demonstrated in one surviving dog that was consistent with the associated resolution of clinical signs. Initial findings in these dogs support further investigation of specific MRI patterns in cases of leukoencephalopathy to aid differential diagnosis. While antemortem detection of bromethalin and its metabolites confirms exposure, quantitation may be informative as a prognostic biomarker.

A hypomyelinating leukodystrophy in German Shepherd dogs

BACKGROUND

Shaking puppy syndrome is commonly attributed to abnormal myelination of the central nervous system.

HYPOTHESIS/OBJECTIVES

To report the long-term clinical course and the imaging characteristics of hypomyelinating leukodystrophy in German Shepherd dogs.

ANIMALS AND METHODS

Three related litters with 11 affected dogs.

RESULTS

The 11 affected dogs experienced coarse, side-to-side tremors of the head and trunk, which interfered with normal goal-oriented movements and disappeared at rest. Signs were noticed shortly after birth. Nine dogs were euthanized, 3 dogs underwent pathological examination, and 2 littermates were raised by their breeder. Tremors improved gradually until 6 to 7 months of age. Adult dogs walked with severe residual pelvic limb ataxia. One dog developed epilepsy with tonic-clonic seizures at 15 months of age. Conventional magnetic resonance imaging (MRI) disclosed homogenous hyperintense signal of the entire subcortical white matter in 3 affected 7-week-old dogs and a hypointense signal in a presumably unaffected littermate. Subcortical white matter appeared isointense to gray matter at 15 and 27 weeks of age on repeated MRI. Abnormal white matter signal with failure to display normal gray-white matter contrast persisted into adulthood. Cerebellar arbor vitae was not visible at any time point. Clinical signs, MRI findings, and pathological examinations were indicative of a hypomyelinating leukodystrophy. All parents of the affected litters shared a common ancestor and relatedness of the puppies suggested an autosomal recessive mode of inheritance.

CONCLUSION

We describe a novel hypomyelinating leukodystrophy in German Shepherd dogs with a suspected inherited origin.