UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory

Mucopolysaccharidosis VII

Mucopolysaccharidosis VII (MPS VII) is a lysosomal storage disease characterized by accumulation of glycosaminoglycans (amino sugars) within cells. Glycosaminoglycans are found in cells involved with development of bone, cartilage, tendons, corneas, skin and connective tissue, and in fluid that lubricates joints. Under normal conditions of cell metabolism, these amino sugars are broken down into simpler sugars by the beta-glucuronidase enzyme encoded by the gene β- glucuronidase (GUSB). Mutations in the GUSB gene disrupt production or activity of this enzyme leading to an accumulation of amino sugars that causes permanent cell damage. MPS VII disease has an early onset and is progressive. By one month of age, affected pups typically show shortened broad faces, low-set ears, and broad chests relative to unaffected littermates. By two months of age, corneal clouding is observed and differential development is apparent with affected dogs being roughly half the size of unaffected siblings. As the disease progresses, standing becomes difficult and joints become swollen and are easily dislocated. Additional clinical signs include cardiac abnormalities, tracheal narrowing, and glycosaminoglycans in the urine.

Two independent, breed-specific mutations in the GUSB gene result in MPS VII disease: c.866C>T in Brazilian Terriers (reported as MPS7bt) and c.497G>A in German Shepherd Dogs (reported as MPS7gs).  In both cases, the disease is inherited in an autosomal recessive fashion, which means that males and females are equally affected and that two copies of the defective gene are needed to cause MPSVII. Dogs with one normal and one affected gene (carriers) are normal and show no signs of the disease.
The Veterinary Genetics Laboratory offers genetic tests for MPS VII. Test results assist veterinarians with diagnosis of MPS VII and help breeders identify carriers among breeding stock to avoid producing affected dogs. Matings between carriers are expected to produce 25% of affected puppies.

Testing is recommended for: Brazilian Terrier, German Shepherd Dog

Allow 5-10 business days for results.

Results reported as:


Normal - no copies of the MPSVII mutation


Carrier - 1 copy of the MPSVII mutation


Affected - 2 copies of the MPSVII mutation

*Report will specify MPS7bt or MPS7gs according to breed and mutation present.


Hytönen MK, Arumilli M, Lappalainen AK, Kallio H, Snellman M, Sainio K, Lohi H. (2012) A novel GUSB mutation in Brazilian terriers with severe skeletal abnormalities defines the disease as mucopolysaccharidosis VII. PLoS One 7:e40281.

Ray J, Bouvet A, DeSanto C, Fyfe JC, Xu D, Wolfe JH, Aguirre GD, Patterson DF, Haskins ME, Henthorn PS. (1998) Cloning of the canine beta-glucuronidase cDNA, mutation identification in canine MPS VII, and retroviral vector-mediated correction of MPS VII cells. Genomics 48:248-253.

Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL