Skip Navigation
Genetics Home Reference: your guide to understanding genetic conditions About   Site Map   Contact Us
Home A service of the U.S. National Library of Medicine®
Printer-friendly version

COG5-congenital disorder of glycosylation

(often shortened to COG5-CDG)
Reviewed August 2014

What is COG5-CDG?

COG5-congenital disorder of glycosylation (COG5-CDG, formerly known as congenital disorder of glycosylation type 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 COG5-CDG 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 COG5-CDG 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 COG5-CDG?

COG5-CDG is a very rare disorder; fewer than 10 cases have been described in the medical literature.

What genes are related to COG5-CDG?

COG5-CDG 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 COG5-CDG. The severity of COG5-CDG is related to the amount of COG5 protein that remains in cells.

Read more about the COG5 gene.

How do people inherit COG5-CDG?

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 COG5-CDG?

These resources address the diagnosis or management of COG5-CDG and may include treatment providers.

You might also find information on the diagnosis or management of COG5-CDG in Educational resources and Patient support.

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 COG5-CDG?

You may find the following resources about COG5-CDG 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 COG5-CDG?

  • carbohydrate deficient glycoprotein syndrome type IIi
  • CDG2I
  • CDGIIi
  • CDG IIi
  • congenital disorder of glycosylation type IIi

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about COG5-CDG?

Where can I find general information about genetic conditions?

What glossary definitions help with understanding COG5-CDG?

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.

Reviewed: August 2014
Published: October 5, 2015