Mucopolysaccharidoses in Cats

Metabolic Disorders Due to Lysomal Enzyme Deficiency in Cats

Mucopolysaccharidoses are a group of metabolic disorders characterized by the accumulation of GAGs (glycosaminoglycans, or mucopolysaccharides) due to the impaired functions of lysosomal enzymes. It is the mucopolysaccharides which help in building bones, cartilage, skin, tendons, corneas, and the fluid responsible for lubricating joints.

Domestic shorthair and Siamese cats are predisposed to mucopolysaccharidoses.

Symptoms and Types

• Dwarfism
• Severe bone disease
• Degenerative joint disease (DJD), including partial dislocation of hip joint
• Facial structural deformity
• Enlarged liver
• Eye cloudiness

Causes

Mucopolysaccharidoses is a genetic abnormality. However, inbreeding increases the risk, especially if the defective gene is present in the family.

Diagnosis

You will need to give a thorough history of your cat’s health, including the onset and nature of the symptoms. He or she will then perform a complete physical examination, as well as a biochemistry profile, urinalysis, and complete blood count (CBC). These tests may reveal valuable information for initial diagnosis, including the presence of characteristic granules within neutrophils and monocytes (types of white blood cells). Your pet’s veterinarian will also take a sample from other body sites and organs -- such as the liver, bone marrow, joints, and lymph nodes -- for further analysis.

Definitive diagnosis, however, is typically made by measuring the lysosomal enzyme levels in blood or liver. Bone X-rays, meanwhile, will reveal decreased bone density and other bone- and joint-related abnormalities.

Treatment

If a bone marrow transplant is conducted at an early age, the cat may be able to live a “near normal” life. However, this treatment is expensive, life-threatening, and not very helpful at a mature age. Also, a healthy donor is required for bone marrow transplant.

Enzyme replacement therapy is effective in cats with mucopolysaccharidoses, but this, too, is an expensive recourse and has not been widely used in animals. Gene therapy, meanwhile, is thought to be an effective method of treatment, and is under evaluation for the treatment both in humans and animals.

Living and Management

Overall prognosis in cats that have undergone bone marrow transplants is usually good. However, as the cat gets older, it will suffer from various problem, including eating difficulties. Therefore, they will require softer and easily palatable foods. Cats with mucopolysaccharidoses are also prone to infections and may require antibiotic therapy.

Due to the genetic nature of this group of disorders, your veterinarian will recommend against breeding cats with mucopolysaccharidoses.