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Congenital disorder of glycosylation type IIi
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Reviewed August 2014
What is congenital disorder of glycosylation type IIi?
Congenital disorder of glycosylation type IIi (CDG IIi) is an inherited condition that causes neurological problems and other abnormalities. The pattern and severity of this disorder's signs and symptoms vary among affected individuals.
Individuals with CDG IIi typically develop signs and symptoms of the condition during infancy. These individuals often have weak muscle tone (hypotonia) and delayed development. Other neurological features include moderate to severe intellectual disability, poor coordination, and difficulty walking. Some affected individuals never learn to speak. Other features of CDG IIi include short stature, an unusually small head size (microcephaly), and distinctive facial features, which can include ears that are set low and rotated backward, a short neck with a low hairline in the back, and a prominent nose. Less commonly, affected individuals can have hearing loss caused by changes in the inner ear (sensorineural hearing loss), vision impairment, damage to the nerves that control bladder function (a condition called neurogenic bladder), liver disease, and joint deformities (contractures).
How common is congenital disorder of glycosylation type IIi?
CDG IIi is a very rare disorder; fewer than 10 cases have been described in the medical literature.
What genes are related to congenital disorder of glycosylation type IIi?
CDG IIi is caused by mutations in the COG5 gene, which provides instructions for making one piece of a group of proteins known as the conserved oligomeric Golgi (COG) complex. This complex functions in the Golgi apparatus, which is a cellular structure in which newly produced proteins are modified. One process that occurs in the Golgi apparatus is glycosylation, by which sugar molecules (oligosaccharides) are attached to proteins and fats. Glycosylation modifies proteins so they can perform a wider variety of functions.
The COG complex takes part in the transport of proteins, including those that perform glycosylation, in the Golgi apparatus. COG5 gene mutations reduce the amount of COG5 protein or eliminate it completely, which disrupts protein transport. This disruption results in abnormal protein glycosylation, which can affect numerous body systems, leading to the signs and symptoms of CDG IIi. The severity of CDG IIi is related to the amount of COG5 protein that remains in cells.
Read more about the COG5 gene.
How do people inherit congenital disorder of glycosylation type IIi?
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 IIi?
These resources address the diagnosis or management of congenital disorder of glycosylation type IIi and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
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 IIi?
You may find the following resources about congenital disorder of glycosylation type IIi 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 IIi?
What if I still have specific questions about congenital disorder of glycosylation type IIi?
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 IIi?
autosomal ; autosomal recessive ; carbohydrate ; cell ; congenital ; disability ; gene ; glycosylation ; Golgi apparatus ; hypotonia ; inherited ; joint ; microcephaly ; muscle tone ; neurological ; oligosaccharides ; protein ; recessive ; sensorineural ; sensorineural hearing loss ; short stature ; stature ; syndrome
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (5 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.