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Aspartylglycosaminuria
Tuesday, 24 August 2004
Tuesday, 23 November 2004

What

Aspartylglycosaminuria is a very rare, inherited disorder that most commonly affects children. It is characterized by the progressive development of abnormal facial features, deformities of the extremities, and mental retardation. This disease is considered to belong to a class of genetic disorders known as lysosomal storage diseases. A common feature of lysosomal storage diseases is the accumulation of toxic substances within cells in the body. One well-known type of lysosomal storage disease is Tay-Sachs disease.

Who

The worldwide incidence of Aspartylglycosaminuria is not known because it is a very rare disorder. Males and females are affected equally and people of Finnish descent are more frequently affected. In Finland, there are an estimated 130 cases per 4.5 million persons.

Signs and Symptoms

Children with Aspartylglycosaminuria may appear normal in the first month of life but will begin to show signs and symptoms in early infancy. All or some of the following may be present:

  • Coarse facial features – thickened skull bones, saggy cheeks, broad nose
  • Shortened neck
  • Hand and feet deformities
  • Abnormal curvature of the spine (scoliosis)
  • Frequent convulsions
  • Enlarged liver and spleen
  • Frequent respiratory infections
  • Progressive mental retardation
  • Changes in behavior.

Possible Causes

Aspartylglycosaminuria is a lysosomal storage disorder that involves a structure within the cell known as a lysosome. Lysosomes function to process waste products in the cell and contain many different enzymes (proteins that digest cellular byproducts). In aspartylglycosaminuria, one of these enzymes called aspartyglucosaminidase is lacking and is needed to help the lysosomes process waste products. This deficiency leads to the accumulation of toxic byproducts that cause cell dysfunction and death. Since most cells contain lysosomes, most organs/structures in the body are affected. The gene defect that leads to aspartylglycosaminuria has been identified and follows an autosomal recessive inheritance pattern. In order to have Aspartylglycosaminuria, a child must receive two bad copies of the aspartylglucosaminidase gene (one from each parent).

Diagnosis

Making the diagnosis of Aspartylglycosaminuria requires the recognition of characteristic facial features and specific genetic tests. Recurrent diarrhea usually prompts families with these children to seek medical attention within the first year of birth. Along with diarrhea, the child may also suffer from frequent infections and even hernias. Blood tests along with urine analysis may be done if this disorder is suspected. The definitive diagnosis of aspartylglycosaminuria is usually made with the presence of aspartylglycosamine in the urine of the child. If there is aspartylglycosamine in the urine, white blood cells or special skin cells called fibroblasts may be taken by biopsy and examined. Examination of these specimens will reveal no aspartylglucosaminidase activity. This evidence will support the diagnosis of aspartylglycosaminuria.

Treatment

There is unfortunately no cure for Aspartylglycosaminuria. Current treatment for aspartylglycosaminuria involves management of symptoms and complications of the disease. Therapies for this disease involve using medications to treat seizures and behavioral problems. Current research is directed towards the use of gene therapy to restore normal levels of this deficient enzyme. If seizures are a problem, imaging studies such at CT (computed tomography) or MRI (magnetic resonance imaging) may be performed to rule-out the presence of any structural lesions in the brain.

Prognosis

While aspartylglycosaminuria is eventually a fatal disease, children can live close to a normal life with the appropriate management of symptoms and complications of the disease. Unfortunately, because there is no cure at this point, most people die from infection. The average life span of a person with aspartylglycosaminuria is about 25-45 years.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Lysosomal Storage Disease Network
Great website that provides information, resources, and services to physicians and patients alike in their efforts to cope with aspartylglycosaminuria.

National MPS (Mucopolysaccharidoses/Mucolipidoses) Society, Inc
A great site includes detailed information about the disease, treatment options, support groups, and ongoing clinical research. Website also provides a comprehensive list of world wide resources for information on aspartylglycosaminuria.

The Canadian Society for MPS and related diseases: Aspartylglycosaminuria
Organization whose purpose is to provide information and support to individuals and their families afflicted with a Mucopolysaccharide (MPS) disease, increase public awareness of MPS diseases, and raise funds to further research into MPS and related diseases.

CLIMB (Children Living with Inherited Metabolic Diseases)
UK Organization dedicated to fighting metabolic diseases through research, awareness and support. This organization provides advice, information and support on all metabolic diseases to children, young adults, and families.

Google Search for Aspartylglycosaminuria

References and Sources

Emedicine.com: lysosomal storage disease http://www.emedicine.com/NEURO/topic668.htm Aronson, N.N. (1999). Aspartylglycosaminuria: biochemistry and molecular biology. Biochim Biophys Acta. 1455(2-3):139-54. Dunder, U. and Mononen, I. (2001) Human leukocyte glycosylasparaginase: cell-to-cell transfer and properties in correction of aspartylglycosaminuria. FEBS Lett. 499(1-2): 77-81.