Mucopolysaccharidosis type VII (MPS VII) is a member of a group of inherited metabolic disorders collectively termed mucopolysaccharidoses (MPSs). The MPSs are caused by a deficiency of lysosomal enzymes required for the degradation of mucopolysaccharides also called glycosaminoglycans (GAGs) within the lysosome. When functioning normally, the lysosomal enzymes break down these GAGs, however when the enzyme is deficient, the GAG build up in the lysosomes causing damage to the bodys tissues. The MPSs share a chronic progressive course with multisystem involvement, several physical features, laboratory findings, and radiographic abnormalities; these include facial coarsening, hepatomegaly, excretion of urinary GAG fragments, and leukocyte inclusion bodies.
Mucopolysaccharidosis type VII (MPS VII) is an autosomal recessive that occurs when certain mucopolysaccharides, specifically dermatan, heparan, and chondroitin sulfates accumulate in lysosomes due to a deficiency of the enzyme beta-glucuronidase. Unlike other lysosomal storage disorders in which patients begin life with a period of normal development, patients with MPS VII have a high incidence of hydrops fetalis . Clinical features of MPS VII vary widely between patients and include short stature, course facial features, hepatosplenomegaly, respiratory difficulties, hearing loss, and mental retardation.
Mutations in the GUSB gene cause deficiency of beta-glucuronidase leading to MPS VII. A pseudodeficiency allele, a mutation that reduce enzyme activity but does not cause disease, has been described  and will be detected by this sequencing analysis. Diagnostic sequencing analysis of the GUSB gene coding region is available for MPS type VII patients and their at-risk relatives on a clinical basis.
For further clinical information about lysosomal storage diseases, including management and treatment, call the Emory Lysosomal Storage Disease Center at (404) 778-8565 or (800) 200-1524.
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- Confirmation of a clinical diagnosis of MPS VII
- Prenatal testing for known familial mutations.
- Assessment of carrier status in high risk family members known mutation analysis.
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
- Mucopolysaccharide screen (urine GAG) (GA)
- Lysosomal enzyme screening panel (LS)
- Known mutation analysis (Custom Diagnostics) is available to test family members.
- Prenatal testing is available for known familial mutations only. Please call the Laboratory Genetic Counselor for specific requirements for prenatal testing before collecting a fetal sample.