Non-Inflammatory Hereditary Muscle Disease in Dogs

Non-inflammatory hereditary myotonia is an abnormal condition characterized by persistent contraction or delayed relaxation of particular muscles of the body. Tightening or "cramping" of muscles is often stimulated by movement or direct muscle contact. This condition results in constant contraction or delayed relaxation of the skeletal muscles (muscles used for movement).

There are two forms of this condition; congenital myotonia (myotonia congenita) and acquired myotonia.

Congenital myotonia is present before or at birth while acquired myotonia can develop later in life – often experimentally induced with ingestion of herbicides.

A painful, hereditary condition, myotonia is the result of chloride channel malformations in dogs. The inability of the chloride channels (which allow for proper conduction of the complex electrical impulses from the nerves to the muscles) to do their work means constant contraction of voluntary muscles (like that of most of the skeletal system). The congenital form of myotonia is often seen in chow chow and miniature schnauzer breeds.  

Common symptoms associated with myotonia congenita include

Voice change

Muscle stiffness

Stiff gait

Difficulty breathing

Difficulty rising or moving

Difficulty swallowing (dysphagia)

Regurgitation, especially after eating

Tongue may protrude from mouth

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