Lysosomal disease due to a defect in β-glucuronidase (GUSB), with generalized accumulation of glycosaminoglycans. It causes multiple dysostosis, corneal opacity, hepatosplenomegaly, heart disease and, in some models, neurological signs. It is the canine form of human Sly syndrome. It is recognized in the German Shepherd and the Brazilian Terrier, with distinct molecular variants.

The German Shepherd (classic variant) and the Brazilian Terrier are the breeds in which it has been described. The carrier frequency in the breeding population is not reliably published (limited data).

- Puppy with failure to thrive\n- Coarse facial features\n- Corneal opacity\n- Multiple dysostosis and thickened joints\n- Hepatosplenomegaly\n- Valvular heart disease and hernias\n- Ataxia and variable neurological signs

Human MPS VII was described in 1972. The canine form was characterized in the German Shepherd, with a variant in GUSB (Ray et al., 1998; PMID 9521879). A distinct variant in the same gene was identified in the Brazilian Terrier (Hytönen et al., 2012; PMID 22815736). The canine models have been used in gene therapy and enzyme replacement trials (Cubizolle et al., 2014).

- Genotype breeders before mating with the breed-specific test\n- Do not cross two carriers of the same variant: 25 % risk of affected homozygotes\n- A carrier may be crossed with a clear dog; offspring intended for breeding must be tested\n- Exclude affected homozygotes from breeding\n- Remember that the molecular variant differs between breeds: use the specific test for each one

Differential diagnosis with other MPS (especially I and VI), with chondrodystrophy, cutaneous mucinosis and other bone dysplasias. Enzyme assay in leukocytes/tissue and molecular study confirm. The molecular variant differs between breeds: use the specific test for each one; a broad panel is useful if there is mixed ancestry.

1. Ray J et al. 1998. Cloning of the canine beta-glucuronidase cDNA, mutation identification in canine MPS VII, and retroviral vector-mediated correction of MPS VII cells. Genomics. PMID: 9521879
2. Hytönen MK et al. 2012. A novel GUSB mutation in Brazilian terriers with severe skeletal abnormalities defines the disease as mucopolysaccharidosis VII. PLoS One. PMID: 22815736
3. Cubizolle A et al. 2014. Corrective GUSB transfer to the canine mucopolysaccharidosis VII brain. Mol Ther. PMID: 24343103
4. OMIA000667 (GUSB)