Congenital myasthenic syndrome / myasthenia gravis-like disease (CHRNE-related) - Heideterrier / Smooth Fox Terrier

What does this test examine?

This genetic test analyses the CHRNE c.1508dup variant in the Heideterrier and Smooth Fox Terrier. The disorder is known as congenital myasthenic syndrome, CMS, inherited neuromuscular transmission disorder and, depending on the variant, myasthenia gravis-like disease. This is the postsynaptic CHRNE form also described as myasthenia gravis-like disease.

What does this mean for the dog?

In CMS, signal transmission between nerve and muscle does not work normally. A young dog can therefore lose muscle strength quickly after exercise, become unsteady, take shorter strides, sit down or lie down. In some forms, signs improve temporarily after rest and reappear when exercise continues. Because CMS is inherited and carriers usually show no clear signs, the variant can remain hidden in a breeding line.

Affected puppies can show absent reflexes, poor coordination of the forelimbs and progressive muscle weakness at a very young age.

Practical value of this test

This test has practical value because it makes an inherited risk variant visible when ordinary observation cannot reliably identify it.

• The result distinguishes clear dogs, carriers and genetically affected dogs.
• Breeders can identify carriers and plan matings that avoid affected puppies.
• The test helps identify hidden risk variants in a line before a dog is used for breeding.
• In young dogs or families with matching signs, the DNA result gives clear direction for follow-up and selection.
• For breed clubs and breeding programmes, the test helps manage inherited risk without unnecessarily excluding valuable lines.

Inheritance and result

The trait is inherited as an autosomal recessive condition. A dog with N/N does not carry the duplication, N/dup is a carrier and dup/dup causes the genetically affected genotype.