CDG syndrome type 1B

Congenital Disorders of Glycosylation Type 1B (CDG-1B) is a rare genetic disorder that affects the process of glycosylation, the attachment of sugars to proteins and lipids. This process is crucial for the proper functioning of various systems in the body. CDG-1B is one of the many types of Congenital Disorders of Glycosylation, which are classified based on the gene that is affected and the specific step in the glycosylation process that is disrupted.

Symptoms and Diagnosis

The symptoms of CDG-1B can vary widely among individuals but often include gastrointestinal problems, such as protein-losing enteropathy, which leads to the loss of proteins through the gastrointestinal tract. Patients may also experience coagulation abnormalities, liver dysfunction, and failure to thrive. Unlike some other forms of CDG, CDG-1B does not typically affect the nervous system.

Diagnosis of CDG-1B is based on a combination of clinical evaluation, biochemical tests, and genetic testing. The biochemical tests can include isoelectric focusing of transferrin, which shows a characteristic pattern in individuals with CDG. Genetic testing can confirm a diagnosis by identifying mutations in the PMM2 gene, which is responsible for CDG-1B.

Treatment and Management

There is no cure for CDG-1B, but some of its symptoms can be managed with treatment. Mannose supplementation has been shown to be an effective treatment for some individuals with CDG-1B, improving protein-losing enteropathy and coagulation abnormalities. Other treatments are symptomatic and supportive, including nutritional support for those with failure to thrive and medical management of liver disease and coagulation disorders.

Genetic and Molecular Basis

CDG-1B is caused by mutations in the MPI gene, which encodes the enzyme mannose phosphate isomerase. This enzyme is crucial for the proper glycosylation of proteins and lipids. Mutations in the MPI gene lead to a deficiency of functional mannose phosphate isomerase, disrupting the glycosylation process and resulting in the symptoms of CDG-1B.

Epidemiology

CDG-1B is a rare disorder, with only a small number of cases reported in the medical literature. It is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected by the disorder.

See Also

• Congenital Disorders of Glycosylation
• Protein-losing enteropathy
• Isoelectric focusing
• Genetic testing

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