inherited danger: inside mucopolysaccharidosis

Posted by Dr. Kim Smyth on Jul 19 2013

Glycosaminoglycans (GAGs) perform many key functions in our pets’ bodies, from maintaining tissue hydration and regulating cell growth to playing important roles in brain development. But when the breakdown of glycosaminoglycans goes awry, it can mean trouble for your dog or cat.

Mucopolysaccharidosis (MPS) is caused by a deficiency in one of the many enzymes needed to breakdown GAGs. In these cases, accumulations of improperly degraded GAGs form inside of our pet’s cells, leading to a variety of clinical signs.

There are several forms of mucopolysaccharidosis in cats and dogs, and they vary in the specific enzyme that is lacking. All forms of MPS have something in common, though – they are all inherited. Below is list of the breeds associated with each form of MPS.

  • MPS I: Domestic shorthair cats, Plott Hounds, Rottweilers
  • MPS II: Labrador Retrievers
  • MPS III: Wirehaired Dachshunds, New Zealand Huntaways, Schipperkes
  • MPS IV: Siamese cats, Domestic shorthair cats, Miniature Pinschers, Welsh Corgis, Miniature Schnauzers, Chesapeake Bay Retrievers
  • MPS VII: Domestic shorthair cats, mixed breed dogs, German Shepherd Dogs, Rat Terriers

Improperly degraded GAGs accumulate in the cells of the skeletal system, nervous system, muscles, heart, eyes, or liver where they interfere with normal function. Depending on the form of MPS, clinical signs range from stunted growth and skeletal deformities to unsteady gait, tremors, and seizures. Changes in the cornea of the eye can also occur if GAGs accumulate there.

Clinical signs may be seen as early as 10 weeks of age and as late as 2 years old. MPS may be suspected by your veterinarian based on clinical signs, and the disease can be found using a urine test. Improperly degraded GAGs will eventually leak out of the cells where they are accumulating and when that occurs, they will spill over into your pet’s urine. Your veterinarian can send a urine sample off for analysis to confirm the presence of MPS in the urine.

Sadly, at this time, there is no treatment or cure for any of the forms of MPS, though patients may live up to five years or more with the disease. Because the disease is hereditary, studies are ongoing to develop breed specific DNA tests to detect disease carriers before breeding. Affected animals should not be bred.