Central nervous system atrophy with cerebellar ataxia (CACA) of the Belgian Shepherd, caused by a deletion in the SELENOP gene (formerly SEPP1) that impairs selenium transport. Affected puppies show progressive ataxia and cerebellar signs. The genetic test is complementary to the neurological examination.

Carriers: 6 % (38 of 631 unaffected Belgian Shepherds); the deletion was absent in 735 control genomes. Outside the index family: limited data.

- Progressive ataxia with young onset\n- Limb weakness\n- Balance disturbances\n- Possible epileptic seizures\n- Loss of coordination\n- Initial preservation of mental state

CACA of the Belgian Shepherd was described clinically as hereditary cerebellar ataxia. Christen et al. (2021) identified the deletion in the SELENOP gene as the cause, with decreased blood selenium concentrations in homozygotes, and estimated the carrier frequency in unaffected Belgian Shepherds at 6 %.

- Genotype breeding animals of all Belgian Shepherd varieties (SELENOP deletion test) before mating.\n- Do not cross carrier×carrier (25 % affected homozygotes); carrier×clear does not produce affected animals.\n- A priority in lines with juvenile ataxia; also rule out SDCA1 (KCNJ10) and SDCA2 (ATP1B2).\n- Record cases with genetic confirmation to estimate the true prevalence.

The differential diagnosis includes other hereditary ataxias and acquired processes (inflammatory, toxic, metabolic). The molecular basis is not fully defined; clinical confirmation relies on the presentation, MRI and the exclusion of other causes. Onset in young animals. Supportive management.

1. Christen M et al. 2021, deleción del gen SELENOP causa atrofia del SNC con ataxia cerebelar en perros (PMID 34339417)
2. OMIA:002367 CACA (SELENOP)