Breeds Affected: New Forest Pony
Samples Accepted: Blood, Hair
Disease Information: Congenital Myotonia is a disorder in which it takes an unusually long period of time for skeletal muscles to relax after contracting. Affected animals show stiffness when moving, particularly when starting to move, and overgrowth (hypertrophy) of the muscles. Predominant signs include a stiff gait, eye retraction and third eyelid protrusion.
Test Information: This mutation test is based on a single base pair change in exon 15 of the CLCN1 gene. Congenital Myotonia is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers.
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 the Online Mendelian Inheritance in Animals website.