Carbohydrate-deficient glycoprotein syndrome

Carbohydrate-deficient glycoprotein syndrome

Carbohydrate-deficient glycoprotein syndrome (CDG) is a group of rare inherited metabolic disorders that affect the glycosylation of proteins. Glycosylation is the process by which carbohydrates are chemically attached to proteins, which is crucial for their proper function. CDG is characterized by a wide range of symptoms and can affect multiple organ systems.

Classification

CDG is classified into different types based on the specific genetic defect and the glycosylation pathway affected. The most common type is CDG type I, which involves defects in the early steps of glycosylation in the endoplasmic reticulum. CDG type II involves defects in the processing of glycoproteins in the Golgi apparatus.

CDG Type I

CDG type I is further subdivided into several subtypes, such as CDG-Ia, CDG-Ib, and others, based on the specific enzyme deficiency. CDG-Ia, also known as PMM2-CDG, is the most prevalent form and is caused by mutations in the PMM2 gene, which encodes phosphomannomutase 2.

CDG Type II

CDG type II includes subtypes such as CDG-IIa, CDG-IIb, and others. These subtypes are caused by defects in enzymes involved in the modification and processing of glycoproteins after they have been synthesized.

Symptoms

The symptoms of CDG can vary widely depending on the type and severity of the disorder. Common symptoms include:

• Developmental delay
• Intellectual disability
• Hypotonia (low muscle tone)
• Ataxia (lack of muscle coordination)
• Seizures
• Liver dysfunction
• Coagulation disorders
• Abnormal fat distribution

Diagnosis

Diagnosis of CDG typically involves a combination of clinical evaluation, biochemical testing, and genetic testing. Biochemical tests may include analysis of transferrin glycosylation patterns using isoelectric focusing or mass spectrometry. Genetic testing can confirm the specific genetic mutation responsible for the disorder.

Treatment

There is currently no cure for CDG, and treatment is primarily supportive and symptomatic. Management may include physical therapy, occupational therapy, and nutritional support. In some cases, specific treatments may be available for certain subtypes, such as mannose supplementation for CDG-Ib.

Prognosis

The prognosis for individuals with CDG varies depending on the type and severity of the disorder. Some individuals may have a relatively mild form of the disease and lead a near-normal life, while others may have severe disabilities and a reduced life expectancy.

Research

Research into CDG is ongoing, with efforts focused on understanding the underlying mechanisms of the disorder, developing new diagnostic methods, and exploring potential therapies.

Also see

• Glycosylation
• Metabolic disorder
• Genetic testing
• Inherited metabolic disorder

Classification
External resources