Congenital Myasthatic Syndrome.

About the congenital defect

Congenital myasthenic syndrome (CMS) causes muscle weakness in Devon Rex and Sphynx cats.

Affected cats show ventroflexion of the head and neck, head bobbing, scapulae protrusion and generalised muscle weakness and fatigability. Signs become evident at three to 23 weeks of age and usually progress slowly or remain static. Moderately to severely affected cats show evidence of more generalised muscle weakness, particularly following exertion, stress or excitement. Typically they have a high-stepping forelimb gait, head bobbing and progressive dorsal protrusion of the scapulae. These cats tire easily with exercise, with progressive shortening of the stride and superimposed tremor. Eventually they collapse in sternal recumbency, typically with the head coming to rest on, or to one side of, their front paws. Affected cats frequently adopt a characteristic 'chipmunk' position, usually with their front legs resting on a convenient object.


The mutation responsible for CMS has recently been discovered by researchers from the Universities of Missouri, California - Davis, California - San Diego, Sydney and Milan. The genetic disease is recessive, meaning that affected cats have two copies of the mutation. Cats with one copy of the mutation (carriers) are not affected, but can pass the mutation to their offspring.

Tests for this recessive disease are available from Langford Veterinary hospital in the UK and UC Davis in the USA.

DNA samples for testing with the results to be submitted in support of registrations must be taken and certified by a vet.
For identification purposes cats must be microchipped prior to testing and the number clearly shown on all documentation and the cat’s own veterinary record.

Congenital Myasthenic Syndrome (CMS) (Previously referred to as Muscular Dystrophy, Myopathy or Spasticity)
Sphynx, Sphynx Varients,  Devon Rex and Devon Rex Variants may be registered on the Active Register with effect from [date of approval] only if they have themselves been genetically tested as normal for the CMS gene, or their parents have been tested normal, or cats on every pedigree line in previous generations have tested normal.

Pedigree line means both parents and four grandparents, eight great-grandparents, sixteen great-great-grandparents and so on, or any combination of the same which is inclusive of both the sire's and dam's ancestors.


Sphynx, Devon Rex Spnynx Vaarients and Devon Rex Variants which have not been genetically tested or which have been genetically tested as carriers of this gene shall be registered on the Non-Active Register or the Genetic Register. Any such cats which are already registered on the Active Register shall be moved to the Genetic Register.
Offspring of cats registered on the Genetic Register may only be registered on the Active Register if they have themselves been genetically tested as normal for this gene.
All other offspring of cats registered on the Genetic Register shall be registered on the Non-Active Register or the Genetic Register.