Myotonia / congenital myotonia (CLCN1-related) - New Forest pony

Myotonia in New Forest ponies

This genetic test detects the CLCN1 variant c.1775A>C that causes congenital myotonia in New Forest ponies. The condition is also known as myotonia congenita or inherited myotonia.

In myotonia, muscles relax too slowly after contraction. Affected ponies can move stiffly, have difficulty starting movement, show muscle tremors or appear temporarily locked after sudden movement. The cause is disturbed chloride channel function in skeletal muscle.

Practical value of this test

• N/N: the tested CLCN1 variant is not detected.
• N/CM: the animal is a carrier and can pass the variant on.
• CM/CM: this genotype causes congenital myotonia.

Because this form is autosomal recessive, the test supports breeding selection: carriers can be identified reliably and carrier-to-carrier matings can be avoided.