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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed December 2008

What is aspartylglucosaminuria?

Aspartylglucosaminuria is a condition that causes a progressive decline in mental functioning.

Infants with aspartylglucosaminuria appear healthy at birth, and development is typically normal throughout early childhood. The first sign of this condition, evident around the age of 2 or 3, is usually delayed speech. Mild intellectual disability then becomes apparent, and learning occurs at a slowed pace. Intellectual disability progressively worsens in adolescence. Most people with this disorder lose much of the speech they have learned, and affected adults usually have only a few words in their vocabulary. Adults with aspartylglucosaminuria may develop seizures or problems with movement.

People with this condition may also have bones that become progressively weak and prone to fracture (osteoporosis), an unusually large range of joint movement (hypermobility), and loose skin. Affected individuals tend to have a characteristic facial appearance that includes widely spaced eyes (ocular hypertelorism), small ears, and full lips. The nose is short and broad and the face is usually square-shaped. Children with this condition may be tall for their age, but lack of a growth spurt in puberty typically causes adults to be short. Affected children also tend to have frequent upper respiratory infections. Individuals with aspartylglucosaminuria usually survive into mid-adulthood.

How common is aspartylglucosaminuria?

Aspartylglucosaminuria is estimated to affect 1 in 18,500 people in Finland. This condition is less common outside of Finland, but the incidence is unknown.

What genes are related to aspartylglucosaminuria?

Mutations in the AGA gene cause aspartylglucosaminuria. The AGA gene provides instructions for producing an enzyme called aspartylglucosaminidase. This enzyme is active in lysosomes, which are structures inside cells that act as recycling centers. Within lysosomes, the enzyme helps break down complexes of sugar molecules (oligosaccharides) attached to certain proteins (glycoproteins).

AGA gene mutations result in the absence or shortage of the aspartylglucosaminidase enzyme in lysosomes, preventing the normal breakdown of glycoproteins. As a result, glycoproteins can build up within the lysosomes. Excess glycoproteins disrupt the normal functions of the cell and can result in destruction of the cell. A buildup of glycoproteins seems to particularly affect nerve cells in the brain; loss of these cells causes many of the signs and symptoms of aspartylglucosaminuria.

Related Gene(s)

Changes in this gene are associated with aspartylglucosaminuria.

  • AGA

How do people inherit aspartylglucosaminuria?

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 aspartylglucosaminuria?

These resources address the diagnosis or management of aspartylglucosaminuria and may include treatment providers.

  • Genetic Testing Registry: Aspartylglycosaminuria (

You might also find information on the diagnosis or management of aspartylglucosaminuria 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 aspartylglucosaminuria?

You may find the following resources about aspartylglucosaminuria 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 aspartylglucosaminuria?

  • AGA deficiency
  • aspartylglucosamidase deficiency
  • Aspartylglucosaminidase deficiency
  • aspartylglycosaminuria
  • glycosylasparaginase deficiency

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 aspartylglucosaminuria?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding aspartylglucosaminuria?

autosomal ; autosomal recessive ; breakdown ; cell ; deficiency ; disability ; enzyme ; gene ; glycoproteins ; hypermobility ; hypertelorism ; incidence ; inherited ; joint ; ocular hypertelorism ; oligosaccharides ; osteoporosis ; puberty ; recessive ; respiratory ; sign

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Aronson NN Jr. Aspartylglycosaminuria: biochemistry and molecular biology. Biochim Biophys Acta. 1999 Oct 8;1455(2-3):139-54. Review. (
  • Arvio MA, Peippo MM, Arvio PJ, Kääriäinen HA. Dysmorphic facial features in aspartylglucosaminuria patients and carriers. Clin Dysmorphol. 2004 Jan;13(1):11-5. (
  • Saarela J, Laine M, Oinonen C, von Schantz C, Jalanko A, Rouvinen J, Peltonen L. Molecular pathogenesis of a disease: structural consequences of aspartylglucosaminuria mutations. Hum Mol Genet. 2001 Apr 15;10(9):983-95. (


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: December 2008
Published: February 1, 2016