Myotonia Congenita (Schnauzer Type)
Affected Genes: CLCN1
Inheritance: Autosomal Recessive
Variant(canFam6):
chr16:7355281: G>A
Breed: Miniature Schnauzer
Schnoodle
Standard Schnauzer
General Information: Myotonia Congenita (Schnauzer Type) is a genetic muscle disorder that causes muscle cells to remain contracted after activity, leading to a range of symptoms. Affected dogs often present signs early in life, typically as puppies begin to walk. They may exhibit a stiff, uncoordinated gait, often described as a “bunny hop,” and may frequently fall. Other notable features include muscle enlargement, abnormal posture, a pronounced upper jaw compared to the lower jaw, and dental anomalies. While episodes of stiffness are generally not painful and can improve with exercise, they may worsen with cold or excitement. Affected dogs might also experience excessive panting, unusual barking, loud breathing, and swallowing difficulties. Despite these challenges, dogs with Myotonia Congenita typically 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 the CLCN1 gene is essential for identifying carriers and affected dogs of Myotonia Congenita (Schnauzer Type). This condition is inherited in an autosomal recessive pattern, meaning that a dog must inherit two copies of the mutated gene, one from each parent, to express the disorder. Carriers, which have only one copy of the mutation, generally do not show symptoms but can pass the mutated gene to their offspring. When breeding, it is crucial to avoid mating two carriers to prevent the risk of producing affected puppies. Each puppy from such a pairing has a 25% chance of developing the disorder and a 50% chance of being a carrier. Genetic testing for the CLCN1 mutation allows breeders to make informed decisions, ensuring the health and vitality of future generations while eliminating the risk of Myotonia Congenita in the breeding population. This practice is vital for maintaining healthy breeds and avoiding the transmission of this debilitating condition.
References:
Bhalerao DP, Rajpurohit Y, Vite CH, Giger U. Detection of a genetic mutation for myotonia congenita among Miniature Schnauzers and identification of a common carrier ancestor. Am J Vet Res. 2002 63(10):1443-1447.
Vite CH, Cozzi F, Rich M, Klide AK, Volk SW, Lombardo R. Myotonic myopathy in a miniature Schnauzer: case report and data suggesting abnormal chloride conductance across the muscle membrane. J Vet Intern Med. 1998 12(5):394-397.
Vite CH, Melniczek J, Patterson D, Giger U. Congenital myotonic myopathy in the miniature schnauzer: an autosomal recessive trait. J Hered. 1999 90(5):578-580.