Mucopolysaccharidosis (MPS) VII is an inherited lysosomal storage disorder. Affected dogs have insufficient activity of the enzyme beta-glucuronidase, which is responsible for breaking down glycosaminoglycans (GAGs). GAGs are an important component of connective tissue. In affected dogs, there is an accumulation of breakdown products in cells causing abnormal growth and function of various organ systems. Clinical signs of MPS VII are most commonly associated with accumulations in the bones and joints. Therefore, affected dogs typically present between 4 to 8 weeks of age with symptoms of bone and joint disease. Affected puppies have disproportionally large heads with short muzzles, broad faces, low-set ears and domed skulls. Other skeletal deformities include broad chests, joint laxity and deformed, crooked legs resulting in an inability to walk by 5 months of age. Affected puppies also have cloudy eyes and are smaller than their normal littermates. Dogs may also present with heart problems. While affected dogs can survive with assistance for several years, they are often euthanized due to a poor quality of life.

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