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Canine Mendelian disease record

Spinocerebellar Ataxia with Myokymia and/or Seizures (KCNJ10-related; SCA)

Spinocerebellar Ataxia with Myokymia and/or Seizures (KCNJ10-related; SCA). Autosomal recessive. Observed in 7 of 266 breeds tested in the Sniff Atlas, with measured carrier frequencies drawn from 242,665 dogs (Donner 2023). Per-dog phenotype outcome depends on penetrance, modifiers, and environment; the carrier frequencies below describe variant prevalence, not disease incidence.

OMIA identifier
OMIA:002089-9615
Autosomal recessive
Source dataset
Sniff Atlas v1.0.1 / DOI
The human connection

A model of human EAST syndrome

This is the canine counterpart of EAST syndrome in people. That makes affected dogs a naturally-occurring model of the human disease, and it is part of why studying dogs moves medicine forward for everyone. It does not mean your dog has the human disease. It means the two share an underlying biology.

In people, the disease is described as: SeSAME syndrome is characterized by seizures, sensorineural deafness, ataxia, intellectual deficit, and electrolyte imbalance (hypokalemia, metabolic alkalosis, and hypomagnesemia).

In humans it is also called: sesame syndrome, SESAMES.

MONDO:0013005 OMIM 612780

Mapped from OMIA via the human disease's OMIM entry to the Mondo Disease Ontology (Monarch Initiative, CC-BY 4.0). Sniff renders this as a model-of link; the canine disease remains the subject of this page.

About this disease

From OMIA's curated record

Documented in OMIA (Online Mendelian Inheritance in Animals). This describes the disease as recorded in the published literature, not a prediction for any individual dog. As of 2026-06-03.

Summary

Ataxia is characterized by uncoordinated movements and represents a relatively non-specific clinical sign. This entry describes ataxia forms that are caused by genetic variants in the KCNJ10 gene. Phenotypically related ataxias in dogs may also be caused by variants in more than 30 other genes (Cocostîrc et al. 2023; Stee et al. 2023, pmid 37341581). Thus locus heterogeneity for this phenotype must be considered. There are currently 2 different KCNJ10 pathogenic variants known in dogs (p.Ile209Met in various Terrier breeds and p.Leu329Pro in Belgian Shepherds). These canine disorders represent models for SeSAME/EAST syndrome in humans (see MIM link above).

Clinical features

Spinocerebellar ataxia with myokymia, seizures, or both (SAMS): "The median age at onset of cerebellar ataxia in 12 dogs was 3 months (range, 2–6 months)" (Gilliam et al. 2014). Ten out of twelve SAMS-affected dogs of the Russell terrier group showed muscle twitches (myokymia). The median age at onset for myokymia was 6 months (range, 3–8 months). Some SAMS dogs developed seizures. (Gilliam et al. 2014). Spongy degeneration with cerebellar ataxia 1 (SDCA1): This phenotype occurs in Malinois dogs and has an earlier age of onset than SAMS. Kleiter et al. (2011) investigated 5 closely related litters with presumed SDCA1 (the KCNJ10:p.Leu329Pro variant was confirmed in only one of the litters, Mauri et al. 2017). Malinois puppies with SDCA1 developed a severe ataxia at 4-7 weeks of age. Affected dogs showed shivering and were unable to start walking without falling. The severe condition resulted in euthanasia at 5-13 weeks of age (Kleiter et al. 2011). Van Poucke et al. (2017) reported another detailed clinical analysis of 3 SDCA1 affected Malinois dogs. One of the dogs was still alive at 1 year of age despite severely debilitating non-ambulatory ataxia. Van Poucke et al. noted ataxia, myokymia and neuromyotonia as well as auditory changes in SDCA1 affected dogs.

Molecular genetics

By whole-genome sequencing a single SAMS affected Russell group terrier (RGT) dog, and comparing that sequence with whole-genome sequence from 81 canid reference genomes, Gilliam et al. (2014) identified 23 missense variants that were homozygous in the affected dog. Of the two variants that occurred in comparative candidate genes, one (KCNJ10:c.627C>G; p.Ile209Met) was shown by subsequent sequencing and genotyping of other dogs to be causal for this subtype of ataxia, namely "spinocerebellar ataxia with myokymia, seizures, or both (SAMS)". Rohdin et al (2015) confirmed these findings and noted that the KCNJ10:c.627C>G (p.Ile209Met) variant also segregates in Smooth-Haired Fox Terriers and related breeds. Gast et al. (2016) confirmed that the KCNJ10 c.627C>G (p.Ile209Met) variant accounts for most (but not all) cases in another cohort of Parson Russell Terriers and in Jack Russell Terriers. A likely causal variant in Malinois dogs with spongy degeneration with cerebellar ataxia 1 (SDCA1), namely a missense mutation in KCNJ10: c.986T>C; p.Leu329Pro, was reported by a Belgian/UK team (Stee et al., 2016; Van Poucke et al., 2017, accepted for publication 29 September 2016). The phenotype in SDCA1 affected Malinois dogs is slightly different from the phenotype in the terriers with SAMS. Mauri et al. (2017; accepted for publication 16 December 2016) reported the same likely causal mutation in this breed.

Pathology

Macroscopically the central nervous system (CNS) and peripheral nervous system (PNS) of dogs carrying the KCNJ10 variants are normal. Based on histopathology, there is apparently some phenotypical variation depending on the breed and report. In Parson Russell Terriers and in Jack Russell Terriers the KCNJ10 c.627C>G (p.Ile209Met) variant is associated with bilateral-symmetrical axonal degeneration in the ventral and lateral funiculi of the spinal cord (Gilliam et al. 2014). Van Poucke et al. (2017) describe a similar axonal degeneration in the ventral funiculi and in the brainstem and cerebellum of Malinois dogs with the KCNJ10: c.986T>C (p.Leu329Pro) variant in association with myelin vacuolisation and additionally axonal changes in the PNS. In comparison, in the descriptions by Kleiter et al. (2011) and Mauri et al. (2017) the neuropathology of affected Malinois dogs is dominated by vacuolisation (spongy degeneration) targeting the cerebellar nuclei, granule cell layer and cerebellar white matter. This vacuolisation is accompanied by axonal degeneration in the brain and spinal cord, which is mainly characterized by the presence of axonal swellings.

Human analog

OMIA links this condition to its human counterpart in OMIM (Mendelian Inheritance in Man), the place to read across to the deeper human literature for the same biology.

Disease · OMIM 612780 Gene · OMIM 602208

Source: OMIA (Nicholas, Tammen & the Sydney Informatics Hub), entry OMIA:002089-9615, doi:10.25910/2AMR-PV70 (CC-BY 4.0).

Signs & cross-references

How it presents

Catalogued in the Mondo disease ontology (the cross-species disease identity used by the Monarch Initiative) as EAST syndrome (MONDO:0013005).

Phenotype terms: Human Phenotype Ontology + Mammalian Phenotype Ontology; disease terms: Mondo (Monarch Initiative). Cross-references curated by OMIA (doi:10.25910/2AMR-PV70, CC-BY 4.0).

The evidence

Published references

The peer-reviewed papers behind this disease, curated by OMIA. Starred entries are OMIA-designated landmark papers. Showing 6 of 23.

  6. Phenotypic and genetic aspects of hereditary ataxia in dogs. · J Vet Intern Med · 2023 · PMID 37341581

References curated by OMIA (Nicholas, Tammen & the Sydney Informatics Hub), doi:10.25910/2AMR-PV70 (CC-BY 4.0). Full list at the OMIA entry.

Predict a litter

Set each parent's status for Spinocerebellar Ataxia with Myokymia and/or Seizures (KCNJ10-related; SCA) and see the odds for their puppies. Single recessive variant, exact Mendelian math.

Parent A
Parent B
NNClear
NmCarrier
NmCarrier
mmAffected
Clear25%
Carrier50%
Affected25%

These are the genetic odds for one known variant, not a promise: a real litter varies around them, and penetrance or other genes can change whether the condition ever appears. Use it to avoid pairing two carriers and to keep a line healthy, not to engineer a dog. Inheritance mode per OMIA.
Your breed

See what Spinocerebellar Ataxia with Myokymia and/or Seizures (KCNJ10-related; SCA) looks like in your dog's breed.
Carrier frequency by breed

Top 6 well-sampled breeds (n ≥ 50)

Maximum per breed across variants in the Donner 2023 cohort, with . The list below is split into well-sampled breeds (n ≥ 50 tested) and small-sample breeds (n < 50, where the Wilson CI typically spans more than 20 percentage points and frequencies should not be compared directly to the well-sampled entries). Frequencies are population-level, not per-litter or per-line.

0%5%10%
Belgian Malinois2.1% · n 1,186
Parson Russell Terrier1.9% · n 181
Russell Terrier0.21% · n 239
Chihuahua<0.1% · n 4,273
Australian Cattle Dog<0.1% · n 982
German Shepherd<0.1% · n 15,648
n = 22,509 dogs · Donner et al. 2023 carrier-screening cohort · Sniff Atlas
Each bar is one well-sampled breed; the whisker is its Wilson 95% CI, and fainter bars have wider intervals. Frequencies are population-level, not per-litter. Carrier status for Spinocerebellar Ataxia with Myokymia and/or Seizures (KCNJ10-related; SCA) is measured; phenotype outcome depends on penetrance and modifiers.
▸ Full table with Wilson 95% confidence intervals
Breed Carrier frequency n tested
Belgian Malinois 2.1% 1,186
Parson Russell Terrier 1.9% 181
Russell Terrier 0.21% 239
Chihuahua <0.1% 4,273
Australian Cattle Dog <0.1% 982
German Shepherd <0.1% 15,648
▸ Also observed in 1 small-sample breed (n < 50)

Frequencies in this section are statistical estimates with wide Wilson 95% confidence intervals (typically >20 percentage points). Treat these as "carriers observed but the true population frequency is not yet measurable" rather than as comparable to the well-sampled entries above.

Breed Estimate n tested
Fox Terrier Toy 3.1% 48

259 additional breeds in the Donner 2023 cohort were tested but showed no carriers.

Penetrance

From genotype to phenotype

Carrier status is not the same as disease status. Penetrance is the fraction of at-risk dogs that develop the phenotype. The Donner 2023 S4 table tracks this for 2 variant(s) underlying this disease in the cohort.

At-risk dogs evaluated
5
Phenotype confirmed
4
Penetrance range
not yet quantifiable

Fewer than 20 at-risk dogs evaluated; too few to state a penetrance figure.

Predicted disease relevance at the per-dog level is UNPROVEN. The carrier frequency is measured; phenotype outcome is governed by penetrance, environment, and modifier loci. Consult a veterinarian for clinical interpretation.

How to cite this record

Citations

If you use this record in published work, cite the Sniff Atlas (the published dataset that carries the breed-level carrier frequencies) and the upstream sources:

  • Sniff Atlas v1.0.1 for the per-breed carrier frequencies:

    Gehring, M. (2026). Sniff Atlas v1.0.1. Zenodo. https://doi.org/10.5281/zenodo.20566358. CC-BY 4.0.

  • OMIA for the disease definition, inheritance, and gene assignment:

    Nicholas, F. W., & Tammen, I. (2024). OMIA. Sydney Informatics Hub, The University of Sydney. https://doi.org/10.25910/2AMR-PV70. Entry: OMIA:002089-9615.

  • Donner et al. 2023 for the breed × variant carrier-frequency cohort:

    Donner, J., Freyer, J., Davison, S., Anderson, H., Blades, M., Honkanen, L., et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics, 19(2), e1010651. https://doi.org/10.1371/journal.pgen.1010651.

Full citation formats (BibTeX, RIS, CITATION.cff) at sniff.world/cite.

Related

Related

Last updated
Sources: Sniff Atlas v1.0.1 · OMIA OMIA:002089-9615 · Donner et al. 2023