Mucopolysaccharidosis Type VI is a lysosomal storage disease caused by a deficiency of an enzyme which is essential in breaking down dermatan and chondroitin sulfates. Cats with one copy of the Mucopolysaccharidosis Type VI Modifier variant (also referred to as the G1558A mutation) and one copy of the Mucopolysaccharidosis Type VI variant (known as the T1427C mutation) display a mild form of the disease expressed as a higher incidence of degenerative joint disease than that experienced by non-affected cats. Clinical signs of disease have not been associated with cats who have one or two copies of the modifier variant (G1558A mutation) and zero copies of the Mucopolysaccharidosis Type VI variant (T1427C mutation). These cats have a normal physical appearance and exhibit normal growth. An incidental finding of increased granularity within white blood cells of cats with two copies of the Mucopolysaccharidosis Type VI Modifier variant has been reported with unknown clinical relevance.

For cats who inherit only the modifier variant, and zero copies of the Mucopolysaccharidosis Type VI variant, no treatment is indicated as clinical signs are unlikely to develop. This applies to cats with one or two copies of the modifier variant. For cats who inherit one copy of both the Mucopolysaccharidosis Type VI Modifier variant and the Mucopolysaccharidosis Type VI variant, maintaining a healthy weight is important in reducing pain associated with degenerative joint disease. Modifications should be made to the environment, such as providing steps or ramps to favorite resting places, soft bedding, litter pans with low sides, litter pans on each floor of the house, and accessible food and water bowls. Medications for pain management and nutraceuticals may be indicated.

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.

Current understanding is that a cat with one or two copies of the modifier variant can be safely bred with a cat with zero, one or two copies of the modifier variant, as long as both cats are clear for the Mucopolysaccharidosis Type VI variant. Please note: It is possible that disease signs similar to the ones caused by the Mucopolysaccharidosis Type VI variant could develop due to a different genetic or clinical cause.