Familial Episodic Hypokalemic Polymyopathy is caused by excessive potassium loss into the urine which results in symptomatic hypokalemia. Clinical signs usually develop by 2 to 10 months of age. The most characteristic sign of the disease is passive ventroflexion of the head and neck, which is almost pathognomonic but not every cat has this distinct presentation and, thus, diagnosis can be difficult. Further signs include skeletal muscle weakness occurring only in the forelimbs while in others the weakness affects mainly the hindlimbs; and, in others still, appendicular weakness may affect all four limbs. Affected cats may also have muscle tremors, head bobbing, lameness, and alterations in gait. Hypokalemia is linked to muscle pain (myalgia) which can have further variable clinical presentations. If the disease is not diagnosed early enough, the cat may develop incapacitating weakness with an inability to walk, seizures, or cardiopulmonary arrest. The disease has a variable, episodic nature and worsens with stress.

Therapy for this disease is highly variable due to the episodic nature of the condition. As most cats showing clinical signs are still capable of eating and drinking, oral potassium replacement therapy is of high consideration for increasing total body potassium deficits. However, in some cats, it may be difficult to re-establish normal potassium levels using oral supplementation alone and so additional therapy and supportive care may be warranted. As stress may be an important trigger, owners of affected cats can provide a lifestyle favorable towards reducing perceived stresses to their cat.

There are many responsibilities to consider when breeding cats. Regardless of test results it is important that your cat is in good general health and that you are in a position to care for the kittens if new responsible owners are not found. For first time or novice breeders, advice can be found at most cat registry websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to be shown. A carrier cat with one copy of the FEHP mutation can be safely bred with a clear cat with no copies of the FEHP mutation. About half of the kittens will have one copy (carriers) and half will have no copies of the FEHP mutation. Kittens in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected kittens. Please note: It is possible that disease signs similar to the ones caused by the FEHP mutation could develop due to a different genetic or clinical cause.