OMIA:000698-9685 : Myotonia in Felis catus (domestic cat)

In other species: dog , horse , pig , taurine cattle , goat , sheep , water buffalo

Categories: Muscle phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 160800 (trait) , 255700 (trait) , 118425 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Probably autosomal recessive

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2014

Cross-species summary: Myotonia congenita

Molecular basis: Using the candidate gene approach, Gandolphi et al. (2014) identified a likely causal mutation as a "c.1930+1G>T transversion [that] altered the 5′ splice site at the junction of exon 16 and intron 16" of CLCN1, These same authors also reported that "In silico translation of the altered transcript predicts the lack of 116 amino acids, from residues 557 to residue 643 of the protein . . . . The predicted premature CLCN1 protein truncation would cause the partial absence of the first highly conserved CBS1 (cystathionine β-synthase) domain and the third dimerization domain p.578Y". Woelfel et al. (2022) investigated a 10 month old affected domestic longhair cat: "A high impact 8‐base pair (bp) deletion across the end of exon 3 and the beginning of intron 3 of the gene CLCN1 was identified ... in the proband. Sanger sequencing was performed to verify the existence of this 8‐bp deletion ... and confirmed that the proband was homozygous for the deletion ... . All phenotypically normal cats in our database of whole genome sequences lacked this deletion. All 96 additional control cats tested by Sanger sequencing were also found to be negative for the deletion." Corrêa et al. (2023) identified "a missense variant (c.991G>C, p.Ala331Pro) in exon 9 of the CLCN1 gene" as likely causal variant for myotonia in "three mixed-breed cats from the same litter."

Clinical features: Clinically, myotonic cats usually have muscle hypertrophy with dimpling after percussion and may appear poorly groomed. Affected cats demonstrate blepharospasm upon testing the palpebral reflex and menace response but have normal mentation. They ambulate with an abnormally short stride and stiff, choppy gait, restricted limb adduction, and they may stiffen and fall in lateral recumbency when startled. Clinical presentation may also include a limited ability to open the jaws, dysphonia, dysphagia, facial spasms, a protruding hypertrophic tongue, and varying degrees of gingivitis and dental disease. (Toll et al., 1998; Gaschen et al., 2004; Gandolfi et al., 2014) Electromyography of these animals demonstrates classical myotonic discharges, seen as repetitive spontaneous “waxing and waning” discharges (Toll et al., 1998; Gaschen et al., 2004). Some cats have been reported to develop respiratory stridor and cyanosis when stressed by handling (Toll et al., 1998). IT thanks DVM student Alexandrea Costanza, who provided the basis of this contribution in May 2023.

Pathology: Muscle histopathology reveals hypertrophy of all muscle fibre types (Hickford et al., 1998; Gandolfi et al., 2014). IT thanks DVM student Alexandrea Costanza, who provided the basis of this contribution in May 2023.

Breeds: Domestic Longhair, Domestic Shorthair.
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
CLCN1 chloride channel, voltage-sensitive 1 Felis catus A2 NC_058369.1 (157182688..157217438) CLCN1 Homologene, Ensembl , NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.

OMIA Variant ID Breed(s) Variant Phenotype Gene Allele Type of Variant Source of Genetic Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
1573 Domestic Longhair Myotonia CLCN1 deletion, small (<=20) Naturally occurring variant Felis_catus_9.0 A2 g.158967085_158967092del p.(L143Qfs3*) NP_001291956.1; published as chrA2:15897085‐15 897 092, coordinates in this table have been verified in Felis_catus_9.0 2022 35815860
1623 Myotonia CLCN1 missense Naturally occurring variant Felis_catus_9.0 A2 g.158976314G>C c.991G>C p.(A331P) NM_001305027.1; NP_001291956.1 2023 37668104
408 Myotonia CLCN1 splicing Naturally occurring variant Felis_catus_9.0 A2 g.158986498G>T c.1930+1G>T NM_001305027.1 2014 25356766 Variant coordinates obtained from or confirmed by EBI's Some Effect Predictor (VEP) tool

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2023). OMIA:000698-9685: Online Mendelian Inheritance in Animals (OMIA) [dataset].


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.

2023 Corrêa, S., Basso, R.M., Cerri, F.M., de Oliveira-Filho, J.P., Araújo, J.P., Torelli, S.R., Salán, L.P.C.D.C., Salán, M.O., Macedo, I.Z., Borges, A.S. :
Hereditary myotonia in cats associated with a new homozygous missense variant p.Ala331Pro in the muscle chloride channel ClC-1. J Vet Intern Med , 2023. Pubmed reference: 37668104. DOI: 10.1111/jvim.16837.
2022 Woelfel, C., Meurs, K., Friedenberg, S., DeBruyne, N., Olby, N.J. :
A novel mutation of the CLCN1 gene in a cat with myotonia congenita: Diagnosis and treatment. J Vet Intern Med 36:1454-1459, 2022. Pubmed reference: 35815860. DOI: 10.1111/jvim.16471.
2014 Gandolfi, B., Daniel, R.J., O'Brien, D.P., Guo, L.T., Youngs, M.D., Leach, S.B., Jones, B.R., Shelton, G.D., Lyons, L.A. :
A novel mutation in CLCN1 associated with feline myotonia congenita. PLoS One 9:e109926, 2014. Pubmed reference: 25356766. DOI: 10.1371/journal.pone.0109926.
2004 Gaschen, F., Jaggy, A., Jones, B. :
Congenital diseases of feline muscle and neuromuscular junction. J Feline Med Surg 6:355-66, 2004. Pubmed reference: 15546767. DOI: 10.1016/j.jfms.2004.02.003.
1998 Hickford, F.H., Jones, B.R., Gething, M.A., Pack, R., Alley, M.R. :
Congenital myotonia in related kittens Journal of Small Animal Practice 39:281-285, 1998. Pubmed reference: 9673904.
Toll, J., Cooper, B. :
Feline congenital myotonia Journal of Small Animal Practice 39:499, 1998. Pubmed reference: 9816575.
Toll, J., Cooper, B., Altschul, M. :
Congenital myotonia in 2 domestic cats Journal of Veterinary Internal Medicine 12:116-119, 1998. Pubmed reference: 9560769.

Edit History

  • Created by Frank Nicholas on 06 Sep 2005
  • Changed by Frank Nicholas on 31 Dec 2015
  • Changed by Imke Tammen2 on 17 Sep 2022
  • Changed by Imke Tammen2 on 27 May 2023
  • Changed by Imke Tammen2 on 07 Sep 2023