Mucopolysaccharidoses in Cats

Mucopolysaccharidoses is a group of five separate lysosomal disorders. Lysosomes are storage sacs within the cells that hold enzymes used to digest large molecules (glycoproteins, lipids, etc.) to later be recycled. When the storage function is note carried out properly (lysosomal storage disease) the enzymes are not present to digest the large molecules and the animal’s cell is left with an accumulation of glycosaminoglycans. These glycosaminoglycans promote cell growth, playing an important role in a feline’s vertebral structure and physiological functions. 

Mucopolysaccharidoses is a condition that is inherited from a cat’s mother and/or father. Mucopolysaccharidoses affects how a cat grows, evident through dwarfism and deformities of the feline’s facial structures. If both parents carry the mucopolysaccharidoses (MPS) gene mutation, the kitten could develop symptoms as early as 6-8 weeks of age and hind-limb paralysis could occur at just eight months. However, if only one parent carries the mutated gene, the infant will appear relatively healthy and may only have minimal skeletal deformities. Mucopolysaccharidoses is incurable and commonly affects domestic shorthair cat breeds, Siamese cats, Ragdolls, and Birmans. 

Mucopolysaccharidoses causes a feline to accumulate a large amount of the cell growth polysaccharide, glycosaminoglycans. These glycosaminoglycans take over the cells of the skin, liver, white blood cells and bone marrow, causing the cat to develop: 

• Facial deformities characterized by small ears, a wide space between the eyes and a flattened face. 
• Skeletal abnormalities 
• Bone degeneration 
• Paralysis 
• Stunted growth 
• Dwarfism
• Mental disorders
• Corneal clouding
• Enlarged liver 
• Thickening of the heart valves
• Reduced flexibility

Symptoms begin to appear early in a cat’s life. At six to eight weeks of age, a crouching posture and facial abnormalities are prevalent. Bone degeneration and limb weakness soon appear as the kitten reaches only eight months of age, but may stabilize within the next leading month.

Types

Mucopolysaccharidoses can be broken down into five separate types, Mucopolysaccharidoses Type I, II, III, VI and VII. The different types are used to define the stage of Mucopolysaccharidoses, with one being the least severe case and five being the most severe. 

Mucopolysaccharidoses in cats is a hereditary disease, passed through the genetic makeup of parent to offspring from generation to generation. The exact cause as to why the mutation is present is unknown, yet inbreeding seems to be the common link. Mucopolysaccharidoses is incurable and commonly affects domestic shorthair cat breeds, Siamese cats, Ragdolls, and Birmans. 

The diagnosis of Mucopolysaccharidoses in cats will begin with an evaluation of your cat’s medical history and breeding background. Mucopolysaccharidoses is a hereditary disorder that begins with the feline’s parents, so if you have any information about your cat’s family tree, it would be helpful to bring that information with you to the appointment. The veterinarian will take some time to discuss your cat’s recent behavior and symptoms, while he assesses her physically through a physical exam.

Mucopolysaccharidoses is a mutation within a cat’s cells, including the blood cells, so your veterinarian will likely examine your cat’s urine (urinalysis) and blood (complete blood cell count, biochemistry profile, and blood smear test). A blood smear test will allow the vet to have a close-up look at the feline’s white blood cells that may have vacuoles and granules present (a clear indication of a cell abnormality). An enzyme test will ultimately pinpoint the diagnosis, as the lysosomal enzyme, which acts disorderly in Mucopolysaccharidoses, can be measured in the liver or blood. Radiographs of the bones may also be done to evaluate the stage or type of Mucopolysaccharidoses your cat has.

At this time, there is no truly effective way to treat Mucopolysaccharidoses in cats, other than those used to cater to the feline’s symptoms. However, felines diagnosed with Mucopolysaccharidoses are good candidates for gene replacement therapy and enzyme replacement therapy. Gene or enzyme replacement therapies are executed through a bone marrow transplant and can be rather expensive. Your veterinarian may recommend surgery instead to give your cat a better quality of life.

Felines with mucopolysaccharidoses can have a positive recovery after replacement therapy, but results may vary. Managing your cat’s mucopolysaccharidoses can prove difficult over time, as bone disease is not uncommon in cats as the feline ages. A cat with this condition will most likely remain in inside cat to prevent injury and a soft diet will be recommended. Any cat diagnosed with mucopolysaccharidoses should not be used as breeding stock, to prevent spreading the mutation. DNA testing for MPS is available at your local laboratory provider, so talk to your veterinarian about testing other cats of the same litter.