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Congenital disorder of glycosylation type Ic
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Reviewed May 2014
What is congenital disorder of glycosylation type Ic?
Congenital disorder of glycosylation type Ic (known as ALG6-CDG) is an inherited condition that affects many parts of the body. The signs and symptoms of ALG6-CDG vary widely among people with the condition.
Individuals with ALG6-CDG typically develop signs and symptoms of the condition during infancy. They may have difficulty gaining weight and growing at the expected rate (failure to thrive). Affected infants often have weak muscle tone (hypotonia) and developmental delay.
People with ALG6-CDG may have seizures, problems with coordination and balance (ataxia), or stroke-like episodes that involve an extreme lack of energy (lethargy) and temporary paralysis. They may also develop blood clotting disorders. Some individuals with ALG6-CDG have eye abnormalities including eyes that do not look in the same direction (strabismus) and an eye disorder called retinitis pigmentosa, which causes vision loss. Females with ALG6-CDG have hypergonadotropic hypogonadism, which affects the production of hormones that direct sexual development. As a result, most females with ALG6-CDG do not go through puberty.
How common is congenital disorder of glycosylation type Ic?
The prevalence of ALG6-CDG is unknown, but it is thought to be the second most common type of congenital disorder of glycosylation. More than 30 cases of ALG6-CDG have been described in the scientific literature.
What genes are related to congenital disorder of glycosylation type Ic?
Mutations in the ALG6 gene cause ALG6-CDG. The ALG6 gene provides instructions for making an enzyme that is involved in a process called glycosylation. Glycosylation is the process by which sugar molecules (monosaccharides) and complex chains of sugar molecules (oligosaccharides) are added to proteins and fats. Glycosylation modifies proteins and fats so they can perform a wider variety of functions. The enzyme produced from the ALG6 gene transfers a simple sugar called glucose to the growing oligosaccharide. Once the correct number of sugar molecules are linked together, the oligosaccharide is attached to a protein or fat.
ALG6 gene mutations lead to the production of an abnormal enzyme with reduced or no activity. Without a properly functioning enzyme, glycosylation cannot proceed normally, and oligosaccharides are incomplete. As a result, glycosylation is reduced or absent. The wide variety of signs and symptoms in ALG6-CDG are likely due to impaired glycosylation of proteins and fats that are needed for normal function in many organs and tissues, including the brain, eyes, liver, and hormone-producing (endocrine) system.
Read more about the ALG6 gene.
How do people inherit congenital disorder of glycosylation type Ic?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of congenital disorder of glycosylation type Ic?
These resources address the diagnosis or management of congenital disorder of glycosylation type Ic and may include treatment providers.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about congenital disorder of glycosylation type Ic?
You may find the following resources about congenital disorder of glycosylation type Ic helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for congenital disorder of glycosylation type Ic?
What if I still have specific questions about congenital disorder of glycosylation type Ic?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding congenital disorder of glycosylation type Ic?
ataxia ; autosomal ; autosomal recessive ; blood clotting ; carbohydrate ; cell ; clotting ; congenital ; deficiency ; developmental delay ; enzyme ; failure to thrive ; gene ; glucose ; glycosylation ; hormone ; hypogonadism ; hypotonia ; inherited ; lethargy ; muscle tone ; oligosaccharides ; prevalence ; protein ; puberty ; recessive ; simple sugar ; strabismus ; syndrome
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (6 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.