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What is Alpha Mannosidosis?

Alpha Mannosidosis is a rare inherited disease that can cause children and adults to suffer from skeletal deformities, coarse facial features, hearing loss, cognitive disabilities, problems with the immune system (which may mean, for example, you catch infections more readily), mental health and behavioural issues.1

What causes Alpha Mannosidosis?

Our DNA is made up of many genes, one of which provides instructions for making an enzyme called alpha-mannosidase. When specific mutations are present on this gene, the enzyme is not produced correctly, which leads to a build-up of oligosaccharides, causing Alpha Mannosidosis.2

This enzyme works in the lysosomes, which are compartments that
digest and recycle materials in the cell. Within lysosomes, the enzyme helps break down sugar molecules called oligosaccharides. These are long chain sugar molecules used in the building of bones, cartilage, skin, tendons and many other tissues in the body.3

In the course of normal life oligosaccharides are continuously recycled. Enzymes help complete these biological processes in the cell. As children and adults affected with Alpha Mannosidosis lack the enzyme alpha-mannosidase, sugars are only partially broken down and over time begin to build up in the body, causing increasing damage to cells. Babies may show little sign of the disease but as more and more cells become damaged by a build-up of sugars, symptoms start to appear.4

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1

First presentation

Recurrent ear infections associated with hearing loss.5
Progressive impairment of mental functions, speech and motor control.6
Hydrocephalus can be present in the first year of life.7

2

2-3rd decade of life

Muscular weakness and ataxia, skeletal abnormalities and destructive poly-arthropathy.8
Neuro-cognitive development is usually arrested and psychiatric disorders may also manifest.9

3

In adulthood

Patients are unable to achieve complete social independence.10
There are very limited data regarding life expectancy in adults.

All about the symptoms of Alpha Mannosidosis?

Due to the hererogeneity of the disease, the symptoms of Alpha Mannosidosis may initially be confused with those of other medical conditions.11 Diagnoses are made by doing a urine analysis12 and by using blood tests to measure enzyme activity in white blood cells.13

It’s important to talk to your doctor about all the symptoms you notice in your child, as your doctor may not think about the possibility of Alpha Mannosidosis. Often, symptoms start with a child feeling weak, getting ear infections, and having issues with hearing properly.1415

The symptoms of Alpha Mannosidosis, like other related conditions, are extremely varied. Some people will have mild to moderate learning difficulties that develop in childhood or adolescence16, while others may have more severe symptoms that develop from a very early age.1718

The wide range of possible symptoms are presented in the diagram below, however affected individuals may not experience all of them.

Signs of Alpha Mannosidosis

  • Facial Appearance
    The facial appearance of children with Alpha Mannosidosis can be normal. However, their faces may be rounder and their heads rather large with a prominent forehead. The neck may be short and the nose broad with a flattened bridge. The lips are often thickened and the hair tends to be coarse. The ears are often large and low-set.36
  • Nose & Throat
    Frequent coughs, colds and throat infections occur in those suffering from Alpha Mannosidosis.37 The tonsils and adenoids often become enlarged and can partly block the airway.38 The neck may be short, which may contribute to the problems in breathing. Typically, the bridge of the nose is flattened and the passage behind the nose is smaller than usual due to poor growth of the bones in the mid-face and thickening of the mucosal lining.39 40
  • Mouth & Teeth
    Individuals with Alpha Mannosidosis may have an enlarged tongue and widely-spaced teeth.41 42
  • Bones & Joints
    Individuals with Alpha Mannosidosis tend to have problems with bone formation and growth.43 This may lead to both bone and neurological problems if nerves are compressed by bone.44 Over time, bone changes in Alpha Mannosidosis tend to be progressive and arthritis may occur from a young age.45 46 Joint stiffness is a common feature of Alpha Mannosidosis and the maximum range of movement of all joints may become limited. Stiffness may cause pain.47
  • Ears
    The majority of individuals suffering from Alpha Mannosidosis will have a degree of hearing loss and are prone to frequent infections.48
  • Spine
    The bones of the spine (vertebrae) normally line up from the neck to the buttocks. Individuals with Alpha Mannosidosis can have poorly formed vertebrae that may not stably interact with each other.49
  • Intellectual Ability
    Almost all individuals with Alpha Mannosidosis experience some learning difficulties,50 related to the progressive storage of oligosaccharides in the brain.51 However, the pattern is very varied. Individuals at the less severe end of the spectrum may have mild to moderate learning difficulties, while others can be significantly retarded even from a young age.52

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