Glycogenosis type IV in cats (GSD IV): symptoms, treatment and prevention

Glycogenosis type IV is a extremely serious genetic disease, fortunately rare, which results in the death of most of the affected kittens in just a few hours after birth, the other victims of GSD IV also eventually dying following the gradual deterioration of their condition. This pathology exclusively affects Norwegian cats, one of the most robust feline breeds. Spotlight on the GSD IV for which there is no no treatment, its symptoms, mode of transmission, diagnosis, and let’s see if it is possible to eradicate this disease through prevention.

Feline type IV glycogenosis: symptoms

A Norwegian cat affected by this genetic disease presents the following different symptoms:

  • Hyperthermia that persists despite taking an antibiotic or a corticosteroid,
  • Tremor of the whole body and limbs,
  • Contractures,
  • A discontinuous apathy,
  • A gait made difficult and insecure due to the rapid atrophy of the kitten’s muscles,
  • Paralysis of the front and rear limbs, none being spared,
  • Cardiac decompensation,
  • A comatose stage.

Kittens affected by type IV glycogenosis die very quickly after their birth, with the exception of a few. But these are doomed to certain death at most within a few months.

GSD IV (glycogenosis type IV): transmission

The mode of transmission of this genetic disease depends on the status of the breeding cats (male and female). So :

  • The cat born of parents both non carriers of a mutated gene copy cannot strictly not be a carrier. As a result, there is no risk that he transmits GSD IV to his offspring.
  • The cat has a 1 in 2 chance of being a carrier and of transmitting GSD IV if it is from a non-carrier cat and a carrier cat one copy of a mutated gene. The disease does not develop but can be transmitted to its offspring.
  • The cat born of two parents each of which carries a copy of the mutated gene a:
    • 1 in 4 chance of not being a carrier,
    • 1 in 2 chance of being a healthy carrier, note that two healthy carrier parents statistically generate 1 in 4 healthy kittens, or 25% of their offspring.
    • 1 in 4 chance of being a carrier of both copies of the mutated gene, thus possibly becoming ill. Either the disease progresses gradually and death occurs between 8 and 14 months

Any owner of a Norwegian cat should know that the dead is inevitable if the animal is homozygous mutated, i.e. if it is carrier of two mutated genes. It occurs within hours or at the latest in the days following birth in most mutated homozygotes. In others, up to the age of 7 months maximum, the phenotype is normal, but the disease progresses gradually thereafter, these kittens then all without any exception present the revealing symptoms. Death inevitably occurs between 8 and 14 months, but very often these cats are euthanized before that age.

At the present time, the frequency of healthy carrier Norwegian cats at European level is unknown. On the other hand, it is established that in the United States, it is 15%.

Feline type IV glycogenosis: diagnosis

It was in 1992 that GSD IV was first described in the United States by the Professor Fyfe who, in 1996, developed screening tests after sequencing the mutation in question. Today, with some hindsight, it is presumed that in France, Norwegian cats who died from an unidentified disease were probably suffering from type IV glycogenosis.

In France, the availability of this genetic test is very recent. It is carried out thanks to the sampling with the brush of oral cells. It is very quick to perform and does not cause any discomfort or pain. It allows the cat to search for the presence of GBE1 mutation (GBE is an enzyme deficient in type IV glycogenosis). It is also essential for detecting a healthy carrier. This is very important since these cats reach adulthood and therefore can reproduce, which represents a great danger for this feline breed.

Of Additional tests are carried out. The veterinarian is looking for a noticeable increase in creatine kinase level (CK) in the blood, confirming the damage to the muscles. This is because CK is a specific enzyme that plays a role in muscle contraction.

Currently, there is no treatment that helps to treat cats with Type IV glycogenosis.

Glycogenosis type IV: prevention

To prevent the transmission of GSD IV from generation to generation, Norwegian cat breeders have a responsibility to get tested each of their cats as well as the descendants that are intended for breeding. Likewise, it is necessary to have a newly arrived Norwegian cat tested in a kennel and to ensure that it has been sterilized. Otherwise, we must not wait to regularize the situation. Necessarily, any cat detected and recognized as a carrier must imperatively be sterilized. Finally, if you want to organize a mating between one of your cats and a cat outside your own kennel, it is crucial to first find out about the latter’s status.

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