What causes Beta-mannosidosis?
Oligosaccharides are chains of sugar molecules used in the building of bones, cartilage, skin, tendons and many other tissues in the body. “Oligo” means a few and “saccharide” is a general term for the sugar part of the molecule. In the course of normal life there is a continuous recycling process of building new oligosaccharides and breaking down old ones. The breakdown and recycling process requires a series of special biochemical tools called enzymes.
People with beta-mannosidosis are missing or are low in an enzyme called beta-mannosidase which is essential in breaking down oligosaccharides. When oligosaccharides are not completely broken down they remain stored in the body. The symptoms of beta-mannosidosis are a result of the build-up of oligosaccharides in the tissues in the body. Babies may show little sign of the disease but as more and more cells build-up of partially broken down oligosaccharides, symptoms start to appear.
How is Beta-mannosidosis inherited?
Beta-mannosidosis is an autosomal recessive disease this means that both parents must carry the same affected gene and each pass this same affected gene to their child.
People probably carry from 5 to 10 genes with mutations in each of their cells. Problems happen when the particular gene is dominant or when a mutation is present in both copies of a recessive gene pair. Genes are the unique set of instructions inside our bodies that make each of us an individual. They are the blueprint for our growth and development, as well as controlling how our bodies function. Genes are carried on structures called chromosomes and it is usual to have 23 pairs. A child will inherit half of the chromosomes from the mother and the other half from the father resulting in 23 pairs. 22 of these pairs look the same in both males and females. Pair 23 are the sex chromosomes, and this is the pair that differ between females and males. The X chromosome is inherited from the mother and the Y chromosome is inherited from the father. More information about inheritance is available here.
For each pregnancy the chances of a baby inheriting beta-mannosidosis are completely independent of whether a previous child was affected with beta-mannosidosis. With each pregnancy there is a 1 in 4 chance that the baby will be affected by beta-mannosidosis.
All parents of children with beta-mannosidosis can benefit from genetic counselling, the counsellor can provide advice on the risk to close relatives and to suggest whether the wider family should be informed. To find out during a pregnancy, if the baby is affected by beta-mannosidosis, screening tests can be arranged early on during a pregnancy for those families who already have a child with beta-mannosidosis. Where only one parent is a carrier, they can opt for carrier screening but it is not 100% reliable or accurate and is not possible in all cases. Amniocentesis and chorionic villus sampling are both available during the pregnancy to find out if the baby is affected by beta-mannosidosis.
How common is Beta-mannosidosis?
It is estimated that nearly 6% of the UK population (around 3.5million people) will be affected by a rare disease at some point in their lives. A single rare disease may affect up to about 30,000 people however the vast majority of rare diseases affect far fewer than this.
Beta-mannosidosis is believed to be a very rare disease, approximately 20 affected people have been reported worldwide. It is difficult to determine the specific incidence of beta-mannosidosis, because people with mild or non-specific symptoms may never be diagnosed.
How are people with Beta-mannosidosis affected?
Signs and symptoms of beta-mannosidosis vary widely in severity, and the age of onset ranges between infancy and teenage years. Almost all people with beta-mannosidosis experience intellectual disability, and some have difficulties in moving around and seizures. In general, there is an increased risk of respiratory and ear infections, hearing loss, speech impairment, swallowing difficulties, poor muscle tone, and reduced sensation. Children may also have distinctive facial features and clusters dark red spots on the skin formed by enlarged blood vessels.
Treatment options for people with Beta-mannosidosis
At present there is treatment for symptoms as they arise, but no cure for the underlying disease. More information on supportive care treatments for people with MPS and related diseases can be found in the treatments section.
Research & Clinical trials for people with Beta-mannosidosis
For an up-to-date list of current UK based trials taking place visit Be Part of Research (resource provided by the National Institute for Health Research). For an international search visit Clinical Trials (resource provided by the U.S. National Library of Medicine). This resource provides information on trial status including recruiting, completed or withdrawn and worldwide trial locations. To find out more about past or current trials speak to your doctor and learn about the risks and potential benefits.
Living with Beta-mannosidosis
The MPS Society is the only UK charity at the forefront of supporting people and families affected by MPS and related diseases. Our extensive support services offers you a wide range of support and resources. The team can advise and sign post you to adequate needs-led support and services in your local area as well as social care, home adaptions, education and much more. The support team can visit you in your home and provide you with vital support and includes an Advocacy Officer based at Belfast City Hospital supporting members in Northern Ireland.
Get involved and support us in the community, volunteer or support fundraising; we are a small charity but with your support we can continue to offer a highly valued and essential service.
What is Beta-mannosidosis?
Beta-mannosidosis is a rare lysosomal storage disease of the glycoprotein family of diseases and is closely related to mucopolysaccharidoses. Beta-mannosidosis is an extremely rare variant of alpha-mannosidosis.