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Mucopolysaccharidosis type VII: causes, symptoms, diagnosis, treatment
Last reviewed: 04.07.2025
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Mucopolysaccharidosis type VII (synonyms: Sly syndrome, lysosomal beta-D-glucuronidase deficiency).
ICD-10 code
- E76 Disorders of glycosaminoglycan metabolism.
- E76.2 Other mucopolysaccharidoses.
Epidemiology
Mucopolysaccharidosis type VII is an extremely rare disease; there are descriptions of several dozen patients in the literature.
Causes and pathogenesis of mucopolysaccharidosis type VII
Mucopolysaccharidosis VII is an autosomal recessive progressive disease resulting from decreased activity of lysosomal beta-D-glucuronidase, which is involved in the metabolism of dermatan sulfate, heparan sulfate, and chondroitin sulfate. The beta-glucuronidase gene, GUSB, is located on the long arm of chromosome 7 - 7q21.ll. 77.8% of mutations in the gene are point mutations. In Russia, no patients with MPS VII have been diagnosed.
Symptoms of mucopolysaccharidosis type VII
Most severe forms of this syndrome manifest from birth with the so-called fatal non-immune fetal edema and can be detected in utero during ultrasound. In other patients, the main clinical symptoms appear from birth in the form of hepatosplenomegaly, signs of multiple dysostosis and thickening of the skin. In less severe cases of the disease, the debut symptoms occur in the first year of life and are similar to those in Hurler syndrome or a severe form of Hunter syndrome. From birth, patients have umbilical or inguinal hernias, patients often suffer from respiratory viral infections and otitis. Coarse facial features of the gargoyle type, skeletal disorders gradually form, and hepatosplenomegaly and corneal opacity occur. Growth retardation, chest deformity of the carinate type and kyphosis of the spine are often noted.
As the disease progresses, there is a delay in psychomotor development, reaching the level of mental retardation. In most cases, instability of the cervical spine is observed with a high risk of developing spinal cord compression. In patients with manifestation of the disease after 4 years, the leading symptoms are skeletal disorders.
Diagnosis of mucopolysaccharidosis type VII
Laboratory diagnostics
To confirm the diagnosis of mucopolysaccharidosis VII, the level of urinary glycosaminoglycan excretion and beta-glucuronidase activity are measured. In the case of mucopolysaccharidosis VII, the total excretion of glycosaminoglycans in the urine increases and hyperexcretion of dermatan sulfate and heparan sulfate is observed. Beta-glucuronidase activity is measured in leukocytes or in skin fibroblast culture using an artificial fluorogenic substrate.
Prenatal diagnosis is possible by measuring beta-glucuronidase activity in chorionic villus biopsy at 9-11 weeks of pregnancy and/or determining the spectrum of glycosaminoglycans in amniotic fluid at 20-22 weeks of pregnancy. For families with a known genotype, DNA diagnostics can be performed in early pregnancy.
Differential diagnostics
Differential diagnostics are carried out both within the group of mucopolysaccharidoses and with other lysosomal storage diseases: mucolipidoses, galactosialidosis, sialidosis, mannosidosis, fucosidosis, GM1 gangliosidosis.
Treatment of mucopolysaccharidosis type VII
No effective methods have been developed. Symptomatic treatment is used.
[ What tests are needed?
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