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• 2: MPS Diseases
  • 2.1: Overview of symptoms
  • 2.2: Overview of treatment
  • 2.3: Which are the MPS Diseases
    • 2.3.1: MPS I
    • 2.3.2: MPS II
    • 2.3.3: MPS III
    • 2.3.4: MPS IVA
    • 2.3.5: MPS IVB
    • 2.3.6: MPS VI
    • 2.3.7: MPS VII
    • 2.3.8: MPS IX
    • 2.3.9: ML I
    • 2.3.10: ML II and III
    • 2.3.11: ML IV
    • 2.3.12: Fucosidosis
    • 2.3.13: Mannosidosis
      • 2.3.13.1: Megan's Story
    • 2.3.14: Sialic Acid Storage Disease
    • 2.3.15: MSD
    • 2.3.16: AGU
    • 2.3.17: Winchester
    • 2.3.18: Geleo Physic Dysplasia
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• 3: Fabry Disease
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Overview of Mannosidosis

Mannosidosis is a rare lysosomal storage disorder of the oligosaccharide family and closely related to the Mucopolysaccharidoses. Alpha-Mannosidosis was first described by Dr Oekermann, from Lund in Sweden, in 1967. There is another variant known as Beta-Mannosidosis which is extremely rare and has produced a wide range of clinical abnormalities in the few patients described with this disorder.

Mannosidosis is an enzyme deficiency disorder which results in defective mannosidase activity and the accumulation of mannose-rich oligosaccharide chains. This accumulation is responsible for many problems that affect individuals with Mannosidosis.

What causes Mannosidosis?

Oligosaccharides are long chains of sugar molecules used in the building of bones, cartilage, skin, tendons and many other tissues in the body. 'Oligo' means a small number and 'saccharide' is a general term for sugar molecule. In the course of normal life there is a continuous process of building new oligosaccharides and breaking down old ones - a recycling process. The breakdown and recycling process requires a series of special biochemical tools called enzymes. Children and adults with Mannosidosis are missing an enzyme called mannosidase. The incompletely broken down mannosidase remain stored inside the cells of the body and begin to build up causing progressive damage. Babies may show little sign of the disease but as more and more cells become damaged by accumulation of oligosaccharides, symptoms start to appear.

How common is Mannosidosis?

The MPS Society which co-ordinates the European Registry for Mucopolysaccharide and Related Diseases has shown that there are 8 affected individuals in the United Kingdom. Although worldwide approximately 200 cases have been reported, there are probably many more patients who are not diagnosed or reported.

Does Mannosidosis affect individuals differently?

There is a wide spectrum of severity. Some individuals with Mannosidosis will have mild to moderate learning difficulties which may develop in childhood or adolescence.

It is important to remember that Mannosidosis is extremely varied in its effects. There are a whole range of possible symptoms but affected individuals may not experience all of them.

How is Mannosidosis inherited?

Genes, inherited from our parents, control how tall we are, the colour of our eyes and skin. Some genes we inherit are 'recessive', that is to say we carry the gene but it does not have any effect on our development. Mannosidosis is caused by a recessive gene. If an adult carrying the abnormal gene has a partner who is also a carrier, there will be one in four chance with every pregnancy that the foetus will inherit the defective gene from each parent and will suffer from the disease. There is a two in three chance that unaffected brothers and sisters of those affeted by Mannosidosis will be carriers. They can be reassured however that, as the disease is so rare, the chance of having a partner who is another carrier is very slight unless the individuals are of the same family.

All families of affected children should seek further information from their doctor or from a genetic counsellor before planning to have more children. There is a more detailed explanation of this complex subject in a booklet available from the MPS Society on the Pattern of Inheritance in MPS diseases. Please visit our Information Resource section.

Can you test for Mannosidosis in pregnancy?

If you have a child with Mannosidosis it is possible to have tests during any subsequent pregnancy to find out whether the foetus is affected. It is important to contact your doctor as soon as you suspect that you may be pregnant if you wish for tests to be arranged. Both amniocentesis and chorionic villus sampling can be used to diagnose Mannosidosis in utero.

Further information

There is a detailed booklet on Mannosidosis produced by the MPS Society in collaboration with parents and doctors drawing on their experience and with reference to medical literature. The booklet includes detailed information on the presentation and clinical management of the disease and treatment options available. Please visit our Information Resource section.

Personal story