UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory
Glycogen Storage Disease type IV (GSD IV) in Norwegian Forest Cats


Norwegian Forest cats can inherit a defective glycogen branching enzyme (GBE) that causes a severe error in glycogen (sugar) storage in cells. Abnormal glycogen accumulates in muscle, liver and neurons causing progressive organ dysfunctions. The disease is inherited as an autosomal recessive trait. Affected kittens may die at or soon after birth, but a few can appear clinically normal till about 5 months of age. These juveniles develop a persistent fever and later show signs of muscle tremors. The signs progress to generalized muscle atrophy and eventual death.

The VGL offers a test to help breeders identify carriers of GSD IV in Norwegian Forest Cats and select mates for breeding to avoid producing affected kittens.

Procedure for collecting a feline DNA sample

Allow 2-6 business days for results.

Results reported as:

Test Result Glycogen Storage Disease Type IV
N/N Normal – No copies of GSD IV mutation are present.

Carrier – 1 copy of GSD IV mutation is present. If carriers are bred together, 25% of offspring are expected to be affected.


Affected – 2 copies of GSD IV mutation are present.

This test is specific for the GSD IV genetic defect that has been identified in Norwegian Forest Cats.

Reference: Fyfe JC, Kurzhals RL, Hawkins MG, et al. (2007) A complex rearrangement of GBE1 causes both perinatal hypoglycemic collapse and late-juvenile-onset neuromuscular degeneration in glycogen storage disease type IV of Norwegian forest cats. Molecular Genetics and Metabolism 90:383-392.

Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL