Aspartylglucosaminuria

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Aspartylglucosaminuria is a lysosomal storage disorder. This means that it affects the ability of enzymes to function correctly. Specifically, the disorder is caused by a problem in the AGA gene. This gene provides instructions for the glycosylasparaginase enzyme which helps with breaking down certain sugars that are attached to certain proteins such as glycoproteins. This process is needed for breaking down large molecules called glycoasparagines. If they are not broken down, glycoasparagines build up in the fluid and tissue of the body which results in progressive damage to the tissues and organs.

We do not know how many people have this disorder. The most affected group has been individuals of Finnish descent. In Finland, it is estimated that 1 to 3 individuals are born with aspartylglucosaminuria each year. This condition is less common outside of Finland, nevertheless, it can affect people from any race or background and affects males and females equally.

Aspartylglucosaminuria primarily affects mental functioning and movement. Signs and symptoms typically develop in early childhood between the ages of 2 and 5 and become progressively worse with age.

Children usually begin to develop:

• Delayed speech
• Mild intellectual disability
• Problems coordinating movementsOther features include:
• Respiratory infections
• Protrusion of organs through gaps in muscles (hernia)
• Growth spurt resulting in a large head size (macrocephaly)
• Bones that become progressively weak and prone to fracture (osteoporosis)
• Unusually large range of joint movement (hypermobility)
• Cardiomyopathy, hypertrophic
• Enlargement of liver and spleen (Hepatosplenomegaly)
• Muscle tightness and stiffness (spasticity)
• Loose skin
• Widely spaced eyes (ocular hypertelorism)
• Small ears
• Full lips
• Nose is short and broad
• Face is usually square-shaped
• Poor oral health, including infections and gum disease (gingivitis).Intellectual disability and movement problems become worse in adolescence. Gradual loss of speech progresses into adulthood. Adults often have psychological disorders and may develop epileptic seizures. The average life expectancy is mid-adulthood.

Diagnosis is based upon a clinical examination by your specialist or doctor. However, as the signs and symptoms of this disorder are similar to other conditions, you will need further tests. Doctors will undertake specialised blood and urine tests. Prenatal detection is possible. DNA tests are needed to confirm the diagnosis.

There is no cure for Aspartylglucosaminuria. There have been attempts at treatment with bone marrow transplants but with inconclusive results. The disorder can be managed by the care provided by a team of multidisciplinary specialists. Rehabilitation, speech and occupational therapy are recommended. Children often require extra support at school and may attend a Special Educational Needs school. Adults often benefit from physiotherapy and music therapy. Regular hearing check-ups are advised due to regular ear infections. Medication may be prescribed for the treatment of epilepsy or insomnia. 

Aspartylglucosaminuria can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier. 

If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have. 

If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.  

Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited Aspartylglucosaminuria. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own. 

Established in 1982, The Society for Mucopolysaccharide Diseases (MPS Society) provides professional support to individuals and families affected by MPS and related Lysosomal Storage Diseases throughout the UK.

MPS Society Contact Details:

• Phone: 0345 389 9901
• Email: mps@mpssociety.org.uk
• Website: https://mpssociety.org.uk/

References are available on request. Please contact us on 0800 652 3181 or by emailing contact@metabolicsupport.org.

Please note calls to 0800 numbers are free from UK landlines and mobiles. Calls from business lines may be charged – please check with your provider.

This information about metabolic diseases is provided by Metabolic Support UK and is intended for educational purposes only. It should not be used for diagnostic or treatment purposes.

Should you require more detailed information please contact Metabolic Support UK by email (contact@metabolicsupport.org) or by telephone ( 0800 652 3181). For specific medical information regarding a disorder or individual please contact your GP or Paediatrician. Metabolic Support UK accepts no responsibility for any errors or omissions nor does Metabolic Support UK assume any liability of any kind for the content of any information contained within this summary or any use that you may make of it.