Congenital Myotonia (CM)
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→ Impaired movement due to muscle rigidity.
Instructions for ordering:
- Enter the information of the first horse for which you want to order the test
- Add to cart
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- Enter the information for a second horse
- For sample collection follow the instructions here.
- You can use this template to send in hair samples.
- Please also send the completed order form together with the samples.
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Any information you include here is optional, but will be included on the certificate of results (except “Aditional Info”).
- Foal may seem healthy when born but symptoms may evolve and worsen over time.
- Symptoms mentioned in the “Symptoms” tap are caused by the general muscle stiffness in the affected horse.
- Difficulties rising
- Gait abnormalities
- Muscular rigidity, especially in hindquarters
- Vertigo and 0ccasional falling
- Impaired flexibility of fetlock joints
- Temporary protruding third eyelid
- Inward protuberant eyeballs
- Excessively muscled
Inheritance and Genotypes
→ CM is an autosomal recessive hereditary disease, meaning that horses with only one copy of the genetic variant (N/cm) are clinically normal carriers while horses with two copies of the genetic variant (cm/cm) are affected.
|Genotype:||The horse is:||Effects:|
|N/N||normal.||The horse does not have any copies of the genetic variant causative for CM and therefore cannot pass it on to any offspring.|
|N/cm||a carrier.||The horse is clinically healthy. It has one copy of the genetic variant causitive for CM, which will be passed on to its offspring with a probability of 50%.|
|cm/cm||affected.||The genetic variant causative for CM will be passed on to all offspring. All offspring will be carriers (N/cm).|
- Carriers may be bred to normal animals (N/cm x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
- Breeding two carriers (N/cm x N/cm) is not recommended due to the possibility of 25% of the offspring being affected.
- Affected animals (cm/cm) should not be used for breeding.
Wijnberg, I.D., Owczarek-Lipska, M., Sacchetto, R., Mascarello, F., Pascoli, F., Grünberg, W., van der Kolk, J.H., Drögemüller, C.: A missense mutation in the skeletal muscle chloride channel 1 (CLCN1) as candidate causal mutation for congenital myotonia in a New Forest pony. Neuromuscul Disord 22:361-7, 2012. Pubmed reference: 22197188. Doi: 10.1016/j.nmd.2011.10.001.
Further information is available at Online Mendelian Inheritance in Animals.