Test Detail

Second form of spongy degeneration with cerebellar ataxia of the Belgian Shepherd, also recessive and described in the Malinois. It shares early onset (4 weeks) and bilateral-symmetrical vacuolation of the neuropil with SDCA1, but adds seizures, circling and central blindness. The rapid progression almost always necessitates euthanasia by around 6 weeks of age.

Described in the Belgian Shepherd Malinois (4 of 11 puppies in the index family). The variant in homozygosity was found in 5 affected dogs and was absent in 258 control Belgian Shepherds and in 503 dogs of other breeds. Population frequency not published: limited data.

- Test breeding dogs before mating in all Belgian Shepherd varieties, with priority in the Malinois
- Do not mate two carriers: 25% risk of affected homozygotes
- A carrier may be mated to a clear dog; the offspring intended for breeding must be tested
- In lines with a neurological history, consider combined SDCA1+SDCA2 testing given the clinical overlap
- Replace carriers with clear offspring without narrowing the gene pool

Clinically indistinguishable from SDCA1 at onset, but with more marked seizures and central blindness. Histology is overlapping (vacuolation in cerebellar nuclei, cervical ventral horn and brainstem, with neuronal necrosis and gliosis). In a Malinois with juvenile cerebellar ataxia, both KCNJ10 and ATP1B2 variants should be tested before confirming the diagnosis. Cases not explained by either variant still exist, suggesting residual genetic heterogeneity.

1. Mauri N et al. 2017, una inserción SINE en ATP1B2 en pastores belgas afectados por degeneración esponjosa con ataxia cerebelar (SDCA2) (PMID 28620085)
2. OMIA:002110 SDCA2 (ATP1B2)