The Norwegian Forest Cat is a natural cat breed. Since the genes have not been significantly modified through artificial breeding, common genetic diseases in purebred cats, such as heart, kidney, eye and respiratory cases, are very rare. The survival temperature of the Norwegian forest cat in its native land reaches minus 16 degrees in winter, and the highest temperature in summer is 24 degrees. It is a cat breed that is afraid of heat but not cold. ​​​​​​

Norwegian Forest Cat Genetic Disease – GSD IV Severely affected kittens will be stillborn or die soon after birth, due to a number of factors affecting the delivery process and the first hour of life. Low blood sugar (not producing enough glucose). In rare cases, infected kittens can develop "normally" until they are 4-5 months old. Infected kittens will have intermittent fever (rising and falling), shivering, and incoordination of movements. Afterwards, the kittens will stop developing. This disease leads to the gradual degeneration of muscles and nerves, severe muscle weakness, atrophy, and limb weakness (especially is the hind legs), loss of appetite, self-cleaning, heart failure, coma, and finally death before the age of 15 months. But kittens are usually euthanized before this age to avoid suffering.

Mutation and inheritance of the GSD IV gene causing glycogen storage disease type 4. The gene that causes glycogen storage disease type 4 GSD IV was discovered by Dr. John Fyfe from the United States. He also developed the gene for the Norwegian Forest Cat in 1996. Genetic testing for genetic mutations. In Europe, this kind of physical examination has been available since 2007. There are 15% reports of this disease in the United States, and statistics in Europe show that 12% of about 2,300 Norwegian forest cats that have undergone medical examinations carry this special gene.

Glycoglycemia type 4 is a very simple autosomal recessive trait, which means that only both parents who carry the mutated gene will have infected offspring.

GSD IV test To prevent kittens from inheriting this mutation, the mutation in the gene encoding the branching enzyme (GBE1) in the Norwegian Forest Cat breed needs to be eliminated from all cats used for breeding , all require DNA testing. The test will tell which cats are healthy but carry the mutated gene. This test only needs to be done once in a lifetime.