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Canine Mendelian disease record

Myotonia Congenita (Discovered in the Australian Cattle Dog)

Myotonia Congenita (Discovered in the Australian Cattle Dog). Autosomal recessive. Observed in 2 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:000698-9615
Autosomal recessive
Source dataset
Sniff Atlas v1.0.1 / DOI
The human connection

A model of human myotonia congenita, autosomal recessive

Dogs with this condition carry a change in CLCN1. In people, changes in the same gene cause myotonia congenita, autosomal recessive. 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: Autosomal recessive form of myotonia congenita.

In humans it is also called: autosomal recessive myotonia congenita, myotonia congenita, recessive.

MONDO:0009715 OMIM 160800OMIM 255700

Mapped from OMIA via the human disease's OMIM entry to the Mondo Disease Ontology (Monarch Initiative, CC-BY 4.0). Closely related human conditions exist for this gene. 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

Myotonia is a chloride channel disorder characterized by delayed skeletal muscle relaxation after contraction. Predominant signs include a stiff gait and skeletal muscle hypertrophy. Genetic tests are available for the miniature schnauzer and Australian cattle dog. Edited by Vicki N. Meyers-Wallen, VMD, PhD, Dipl. ACT

Clinical features

Signs in miniature schnauzers include a stiff gait most pronounced at the onset of movement and during rapid changes in posture (turning quickly, falling), which may diminish with exercise. Other signs include severe skeletal muscle hypertrophy, difficulty rising, increased respiratory sounds, difficulty swallowing, and ptyalism beginning around 2 to 3 months of age. Associated superior prognathism may be a closely segregating trait (Gracis et al., 2000). Signs in the Australian cattle dog are similar, including skeletal muscle hypertrophy and generalized stiffness (Finnigan et al., 2007).
Two French bulldogs reported by Shelton et al. (2024) presented with muscle hypertrophy, swallowing disorders, and gait abnormalities.

Molecular genetics

By cloning and sequencing a very likely comparative candidate gene (based on the homologous disorder in himans, goats and mice), Rhodes et al. (1999) identified a causative variant [omia.variant:62]in the miniature schnauzer as a C to T substitution that changes the amino acid from threonine to methionine [p.T268M] in the CLCN1 gene, which encodes the skeletal muscle voltage-dependent chloride channel. By using the same functional candidate gene approach, Finnigan et al. (2007) identified a causative variant in an Australian cattle dog as a single base pair insertion (g2665insA) in the CLCN1 gene [omia.variant:609], "which would result in a frameshift with a stop codon 51 base pairs (bp) downstream. This mutation effectively truncates [CLCN1] after amino acid 888 (of 977)". Quitt et al. (2018): "Whole exome sequencing [of an affected Labrador Retriever puppy] revealed a case-specific homozygous variant in CLCN1, c.2275A > T resulting in a premature stop codon, p.R759X [omia.variant:1041]. The CLCN1 variant was absent from the genomes of 127 Labrador Retriever controls and 474 control dogs from other breeds." Rodrigues et al. (2020) investigated CLNC1 as a candidate gene in an American Bulldog with hereditary myotonia: "The molecular analysis revealed a frameshift mutation NM_001003124.2:c.436_437insCTCT that resulted in a frameshift and a premature stop codon NP_001003124.1:pTyr146SerfsTer49 [omia.variant:1364]. Two aberrant alternative CLCN1 transcripts were observed in an affected dog, the expected transcript with the 4 bp insertion, NM_001003124.2:r.436_437insctct, and an unexpected transcript containing parts of intron 6 in addition to the insertion in exon 4, NM_001003124.2:[r.436_437insctct;r.774_775ins79]." Chimenas et al. (2023) "describe ... a complex CLCN1 variant in a mixed-breed dog with clinical and electromyographic signs of HM. ... After sequencing the CLCN1 gene, a complex variant was found in exon 6 c.[705T>G; 708del; 712_732del; omia.variant:1570], resulting in a premature stop codon in exon 7 and a protein that was 717 amino acids shorter than the normal CLC protein. The myotonic dog was identified as homozygous recessive for the complex CLCN1 variant; its parents were heterozygous, and its male littermate was homozygous wild-type."
Shelton et al. (2024) investigated "two young French bulldogs with dysphagia and increased muscle mass in the shoulder and neck ... ." The authors conducted whole genome sequencing analysis and identified "a homozygous 8 bp duplication insertion variant in the CLCN1 gene [omia.variant:1678] resulting in a frameshift and premature stop codon (NP_001003124.1. p. F811Lfs*39) ... ."
Eguchi et al. (2024) reported a male mixed breed dog with inherited myotonia: "Genetic testing of the myotonic patient identified a complex of mutations, including c.[1636_1639 delins AACGGG] and c.[1644 A>T] [omia.variant:1757], both located in exon 15 of the CLCN1 gene leading to the formation of a premature stop codon." 

Pathology

In affected dogs, skeletal muscle voltage-dependent chloride channels are unable to fully open at voltages near the resting membrane potential. There is a resultant delay in skeletal muscle relaxation after termination of the action potential, as depolarization is maintained longer than normal. Spontaneous triggering of action potentials independent of neuromuscular signaling induces frequent contraction and muscle hypertrophy (Rhodes et al., 1999).

Prevalence

Of 372 Miniature schnauzers tested from the US, Canada, Europe and Australia, 78.5% were normal, 20.4% were carriers, and 1.1% were affected. All affected dogs initially identified had a common ancestor (Bhalerao et al., 2002).

Inheritance

Although heterozygotes have heterodimeric chloride channels in their skeletal muscle, they appear clinically normal (Rhodes et al., 1999). Rodrigues et al. (2020) "The family history and pedigree analysis suggested an autosomal recessive inheritance pattern [in American Bulldogs]...."

Control

Siblings of affected dogs and relatives of their parents should be tested. Breeding of affected dogs or carriers is discouraged.

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 160800 Disease · OMIM 255700 Gene · OMIM 118425

Source: OMIA (Nicholas, Tammen & the Sydney Informatics Hub), entry OMIA:000698-9615, 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 Thomsen and Becker disease (MONDO:0009710).

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 30.

  1. ★
    Genetic panel screening of nearly 100 mutations reveals new insights into the breed distribution of risk variants for canine hereditary disorders. · PLoS One · 2016 · PMID 27525650

    Why is this an OMIA Landmark paper? It is "the first large scale report of DNA panel screening across purebred dogs to date", involving the genotyping of 6,788 dogs from 233 breeds for 93 disease-implicated variants across 80 single-locus disorders, providing a very informative "snapshot" of the distribution and frequency of these variants. Importantly, the results indicated "15 risk variants in a total of 34 breeds in which their presence was previously undocumented", which will be very helpful in the provision of genetic counselling in those breeds. The detection of some of these latter variants led to "plausible molecular explanations" for disorders in some breeds.

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 Myotonia Congenita (Discovered in the Australian Cattle Dog) 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 Myotonia Congenita (Discovered in the Australian Cattle Dog) looks like in your dog's breed.
Carrier frequency by breed

Top 2 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%1%2%
Border Collie0.22% · n 6,714
Schnauzer Miniature<0.1% · n 4,638
n = 11,352 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 Myotonia Congenita (Discovered in the Australian Cattle Dog) is measured; phenotype outcome depends on penetrance and modifiers.
▸ Full table with Wilson 95% confidence intervals
Breed Carrier frequency n tested
Border Collie 0.22% 6,714
Schnauzer Miniature <0.1% 4,638

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

Scope of this record

Scope

This record carries the breed-level carrier frequencies from the Donner 2023 cohort. Penetrance data (the fraction of at-risk dogs that develop the phenotype) is not yet quantified for this disease in the Sniff Atlas v1.0.1. The OMIA entry is the authoritative reference for the clinical phenotype, inheritance pattern, and gene assignment.

Predicted disease relevance at the per-dog level is UNPROVEN. The carrier frequency is measured; phenotype outcome depends on 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:000698-9615.

  • 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:000698-9615 · Donner et al. 2023