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Frequently asked questions about Alpha Mannosidosis

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  • What is Alpha Mannosidosis? What causes it?

    Alpha Mannosidosis is a rare hereditary disease that can cause children and adults to suffer from skeletal deformities, coarse facial features, hearing loss, mental retardation, problems with the immune system, psychiatric disorders, and behavioural problems.1

    When the gene that provides instructions for making the enzyme alpha-mannosidase does not function properly, the enzyme is not produced correctly, 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 long chains of sugar molecules (oligosaccharides). Oligosaccharides are used in the building of bones, cartilage, skin, tendons and many other tissues in the body.34

    In people with Alpha Mannosidosis, partially broken down sugars remain stored in the body and build up over time. This causes increasing damage to the cells.5 Babies may show little sign of the disease but as more and more cells become damaged by accumulation of oligosaccharides, symptoms start to appear.6

  • What are the symptoms of Alpha Mannosidosis?

    The symptoms of Alpha Mannosidosis, like other related disorders can be very variable.7

    It is a progressive disease, which shows itself in a variety of ways over a period of time.8

    Because it has such a wide range of symptoms, and as each individual will experience their own unique pattern of symptoms, diagnosis can take a long time.9

    During the first decade of life, a child with the condition may have frequent infections, hearing problems, distinctive facial features and developmental delay.1011

    Parents might notice that their child may have some muscle weakness.12 There may be an unusual feature such as a club foot, a large head, unusual appearance, maybe a bent back. A child may have attention problems and struggle with hearing.1314 One symptom could be a one-off, but the combination of symptoms at the same time is no coincidence. Consider all the symptoms, and seek referral to a metabolic specialist by asking your family doctor to refer you.

    In their 20s and 30s, an adult may experience bone problems and difficulties with movement, such as joint problems, swelling, an unsteady gait and muscle weakness. Ultimately, patients may become dependent on a wheelchair, as they can no longer walk on their own.15

    There may be behavioural or psychiatric problems, which can present as episodes of confusion, sometimes with anxiety, depression or hallucinations.16

    Independent living will be difficult, and Alpha Mannosidosis patients may become socially isolated.1718 The long-term forecast for the condition is poor.19

    • 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.3
    • Nose & Throat
      Frequent coughs, colds and throat infections occur in those suffering from Alpha Mannosidosis.1 The tonsils and adenoids often become enlarged and can partly block the airway.3 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.1,3
    • Mouth & Teeth
      Individuals with Alpha Mannosidosis may have an enlarged tongue and widely-spaced teeth.1,3
    • Bones & Joints
      Individuals with Alpha Mannosidosis tend to have problems with bone formation and growth.3 This may lead to both bone and neurological problems if nerves are compressed by bone.3 Over time, bone changes in Alpha Mannosidosis tend to be progressive and arthritis may occur from a young age.1,3 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.3
    • Ears
      The majority of individuals suffering from Alpha Mannosidosis will have a degree of hearing loss and are prone to frequent infections.1
    • 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.3
    • Intellectual Ability
      Almost all individuals with Alpha Mannosidosis experience some learning difficulties,1 related to the progressive storage of oligosaccharides in the brain.7 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.1
  • Are there different types of Alpha Mannosidosis?

    Three clinical subtypes have been proposed:37

    • Type 1 – A mild form, recognized after ten years of age, with very slow progression, and absence of skeletal abnormalities.
    • Type 2 – A moderate form, recognized before ten years of age, with presence of skeletal abnormalities, slow progression, and development of ataxia at age 20-30
    • Type 3 – A severe form, immediately recognized with skeletal abnormalities and obvious progression leading to early death from progressive central nervous system involvement or myopathy

    However, given the variety of mutations that have been documented, the broad range and severity of symptoms, and no link of particular mutations to clinical subtype, the disease is considered clinically as a continuum from mild to severe.3839

  • How does a person get Alpha Mannosidosis? Is it hereditary?

    Alpha Mannosidosis is inherited, meaning it runs in families.40

    Genes are inherited from our parents. We inherit a copy of each gene from each parent. Some genes we inherit are “recessive”, which means that both copies of that gene need to be inherited for it to have any effect on our development.4142

    Alpha Mannosidosis is caused by a recessive gene.43 If an adult carrying the abnormal gene has a partner who is also a carrier, there will be a 25% chance with every pregnancy that the baby will inherit the defective gene from each parent and will suffer from the disease. There is a two out of three chance that unaffected brothers and sisters of those affected by Alpha Mannosidosis will be carriers.4445

    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.46 If a couple already has a child with the condition, genetic counselling is recommended, to understand the chances of the disease also occurring in future offspring.47

  • How common is Alpha Mannosidosis?

    The prevalence of Alpha Mannosidosis is not known exactly. However, a number of reports from different countries estimate that it occurs in approximately one in every million babies born worldwide.48

  • How is Alpha Mannosidosis diagnosed and by whom?

    Your doctor can use a number of very simple tests to diagnose Alpha Mannosidosis, including:

    1. A physical check-up with medical history.49 If a diagnosis of Alpha Mannosidosis is suspected, your doctor may take urine and blood samples to rule out other clinical conditions and confirm a diagnosis.
    2. Urine sample.50 This will measure oligosaccharide levels in urine. High levels will be suggestive of Alpha Mannosidosis.
    3. Blood sample.51 A small sample of blood is taken to measure the presence of mannosidase enzyme in blood cells. This can be used to confirm a diagnosis.
    4. Genetic testing.52 A diagnosis of Alpha Mannosidosis can also be confirmed through genetic testing, which can detect the mutation in the gene that causes the disorder.
  • Where can I find out about support groups for Alpha Mannosidosis families?

    There’s a supportive community out there that’s eager to provide information sources, understanding and advice. A host of organisations and support groups is just a few clicks away.

    Patient organisations:

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  • How is Alpha Mannosidosis treated?

    A diagnosis of Alpha Mannosidosis can have a considerable emotional impact on patients and caregivers. Access to primary and specialty care and social services needs to be provided, and nutritional and psychological support should be assessed on an ongoing basis.53 Clinical care should be proactive, with doctors planning to limit the consequences of the condition and any complications for patients.54 Joint or other orthopaedic surgery may be considered.55 For more information on management options, please discuss with your doctor.

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