Myotonia Congenita (Australian Cattle Dog Type)

General Information: Myotonia Congenita (MC) (Australian Cattle Dog Type) is a genetic muscle disorder that results in over-excitability of muscle cells, causing muscles to remain contracted instead of relaxing after voluntary activity. This condition typically presents in puppies as they begin to walk, characterized by a stiff, uncoordinated gait and frequent falls. Affected dogs often exhibit a distinctive “bunny hop” gait and muscle stiffness, which may worsen with excitement or hot weather but can improve with regular exercise. Additional symptoms include muscle enlargement, particularly in the neck and limbs, abnormal posture, and a pronounced difference in jaw length, where the upper jaw is notably longer than the lower jaw. Despite these challenges, dogs with Myotonia Congenita generally have a normal lifespan.

How to Read Your Dog's Test Results for this Genetic Variant:

Two Variants Detected: Dog Likely Affected

One Variant Detected: Dog Unlikely Affected

No Variants Detected: No Effect

Gene / Testing Information: Genetic testing for Myotonia Congenita (Australian Cattle Dog Type) involves screening for mutations in the CLCN1 gene. This disorder follows an autosomal recessive inheritance pattern, meaning a dog must inherit two copies of the mutated gene (one from each parent) to develop the disease. Carriers, which have one copy of the mutation, do not display symptoms but can pass the gene to their offspring. When two carriers are bred, there is a 25% chance of producing affected puppies and a 50% chance of producing carriers. Genetic testing is crucial for responsible breeding practices, enabling breeders to identify carriers and avoid breeding them together. By ensuring that at least one parent in a breeding pair is free from the mutation, breeders can significantly reduce the risk of producing affected puppies, thereby promoting the health and genetic integrity of the breed.