Congenital Disorders of Glycosylation Type Ia

Search Knowledgebase

Topic Contents

Congenital Disorders of Glycosylation Type Ia

National Organization for Rare Disorders, Inc.

It is possible that the main title of the report Congenital Disorders of Glycosylation Type Ia is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • CDGS Type Ia
  • CDG1A
  • Hypoglycosylation Syndrome Type Ia
  • Disorder of N-Glycan Synthesis Ia

Disorder Subdivisions

  • None

General Discussion

Since the original publication of the NORD report on this disorder, the standard name was changed from "carbohydrate-deficient glycoprotein syndrome" to "congenital disorders of glycosylation syndrome (CDGS)". CDGS refers to a group of rare inherited metabolic disorders that share similar but not identical genetic changes (mutations) and biochemical characteristics. These disorders involve the metabolic activity of glycoproteins, complex chemical compounds created by attaching a simple or complex sugar molecule (glycolization) to a specific protein. Glycoproteins play key roles in the development and maintenance of the cell membrane, endocrine glandular function, and protein transport, and are active in specific parts of the brain (Golgi apparatus). Attaching the sugar to the protein is a process involving many enzymes, and a shortage or lack of any one of these enzymes causes the build-up of intermediate chemical compounds. The accumulation of these compounds is the triggering device of the disorder. Congenital disorders of glycosylation may affect many different parts of the body but are most serious when they involve the central and peripheral nervous systems.

Recently, medical researchers have agreed to classify the disorder into two major groups. This is based on the chemical pathway in which the defect occurs (mutation leading to an enzyme failure). For the sake of clarity, the disorders that are a result of a faulty enzyme before the sugar molecule is attached to the protein (upstream) are known as Type I disorders. The disorders that arise due to failure in the metabolic process after the sugar molecule has been attached to proteins are known as Type II disorders.

There appear to be 12 distinct disorders (subtypes) within Type I and there are 5 distinct disorders within Type II. Of all the CDGS disorders, regardless of type, CDGS Type Ia comprises about 70% of all cases.

Glycoproteins have several important functions in the body. They play a role in the complex chemical processes that enable the body to function normally. Examples include signaling how cells in the body are to interact with one another, participating in the transfer of nutrients from one part of the body to another (transport), playing a role in the proper coagulation of blood, functioning as hormones that regulate certain organs or activities in the body (i.e., endocrine activities that help to regulate the rate of growth, sexual development, and/or metabolism), etc.

CDGS Type Ia affects several different organ systems. Especially affected are the central nervous system (i.e., the brain and spinal cord), the peripheral nervous system (i.e., motor and sensory nerves outside the central nervous system), and the liver, in which many of the glycoproteins in the blood are made. Although the severity and range of symptoms may vary from case to case, most affected individuals exhibit severe delays in the acquisition of skills that require the coordination of mental and muscular activity (psychomotor retardation); moderate to severe mental retardation; impaired coordination and balance (cerebellar ataxia) due to underdevelopment (hypoplasia) of certain portions of the brain (cerebellum); impaired nerve transmission to the legs, resulting in progressive, severe muscle thinning and weakness (peripheral neuropathy); skeletal malformations; and/or visual and/or hearing impairment. CDGS Type Ia is inherited as an autosomal recessive genetic trait.


Children Living with Inherited Metabolic Diseases (CLIMB)
Climb Building
176 Nantwich Road
Crewe, Intl CW2 6BG
United Kingdom
Tel: 0845 241 2174
Tel: 800 652 3181

Vaincre Les Maladies Lysosomales
2 Ter Avenue
Massy, 91300
Tel: 01 69 75 40 30
Fax: 01 60 11 15 83

Lighthouse International
111 E 59th St
New York, NY 10022-1202
Tel: (800)829-0500

National Association for Parents of Children with Visual Impairments (NAPVI)
P.O. Box 317
Watertown, MA 02272-0317
Tel: (617)972-7441
Fax: (617)972-7444
Tel: (800)562-6265

United Leukodystrophy Foundation
2304 Highland Drive
Sycamore, IL 60718
Fax: (815)895-2432
Tel: (800)728-5483

American Speech-Language-Hearing Association
10801 Rockville Pike
Rockville, MD 20852
United States
Tel: (800)498-2071
Fax: (301)296-8580
Tel: (800)638-8255
TDD: (301)296-5650

NIH/NationaI Institute of Arthritis and Musculoskeletal and Skin Diseases
Information Clearinghouse
One AMS Circle
Bethesda, MD 20892-3675
Tel: (301)495-4484
Fax: (301)718-6366
Tel: (877)226-4267
TDD: (301)565-2966

NIH/National Institute of Neurological Disorders and Stroke
P.O. Box 5801
Bethesda, MD 20824
Tel: (301)496-5751
Fax: (301)402-2186
Tel: (800)352-9424
TDD: (301)468-5981

CDG Family Network
PO Box 860847
Plano, TX 75074
Tel: (800)250-5273

Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311
TDD: (888)205-3223

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc. ® (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site or email

Last Updated:  3/31/2008
Copyright  1996, 1997, 1998, 2006 National Organization for Rare Disorders, Inc.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.