Leukodystrophy

Leukodystrophy is not a single condition but rather refers to a group of conditions that mainly affect the white (‘leuko’) matter of the brain and the spinal cord. The primary leukodystrophies affect myelin production or breakdown. Myelin is the substance that surrounds and insulates the nerve fibres in the nervous system. When myelin is damaged, the underlying nerve tissue cannot operate in the regular way.

Leukodystrophies are usually progressive conditions, which means they get worse over time. They cause loss of normal brain functions. There is no cure, but treatment can help manage some of the symptoms. Life expectancy depends on the type of leukodystrophy.

Symptoms
The symptoms can vary. It depends on how quickly damage to the white matter occurs, which parts of the brain (or spinal cord) are affected and, sometimes, how much the peripheral nerves are affected. The white matter has a large role in motor function (movement), so damage usually leads to problems in this area.

Symptoms often appear in early childhood. They can include subtle or gradual changes to:

• Muscle tone
• Body movements
• Walking style
• Speech
• The ability to chew and swallow food
• Eye sight
• Hearing
• Mental ability
• Behaviour.

• Adrenoleukodystrophy (ALD) – this is one of the more common of the leukodystrophies. Typically, it only affects boys. It is due to an X-linked gene. Symptoms of the childhood cerebral form typically begin before 10 years of age and may progress rapidly. The adrenal glands may also be affected, which means not enough cortisone is produced. The same genetic change can lead to adrenomyeloneuropathy in adults. This form typically affects the spinal cord and the adrenal glands. Female carriers of the gene may show similar but usually much milder symptoms. In some with the same genetic change, the adrenal gland may be affected in isolation.
• Metachromatic leukodystrophy (MLD) – this is another common leukodystrophy. It has a range of subtypes, some of which relate to the age when symptoms appear – for example, late infantile MLD, juvenile MLD and adult MLD. In the infantile form, a loss of motor (movement) and verbal skill may be the first signs. Symptoms typically become progressively worse.
• Canavan’s disease (spongy degeneration) – this form causes abnormal myelin growth. The typical form is characterised by poor head control, decreased tone, regression and a markedly enlarged head. Eventually the decreased tone changes to stiffness. Life expectancy is limited.
• Krabbe disease (globoid leukodystrophy) – this affects the myelin of the central and peripheral nervous systems. About 90 per cent of those affected are babies and symptoms usually show up before they are six months old. There is also a rare adult form.

• Autosomal recessive – the child can only inherit the disorder if both parents are carriers of the gene. Boys and girls are equally affected. The carrier parents won’t have any symptoms, but each of their children will have a one in four chance of developing leukodystrophy and a one in two chance of being a carrier themselves.
• X-linked – the gene is carried on the X-chromosome. The X-chromosome gene is involved in determining the baby’s sex. Men have an X and a Y chromosome and women have two X chromosomes. Because men only have a single copy of the genetic programs on the X-chromosome, if there is a genetic change there are no other genes to compensate. Boys and girls are therefore affected differently.
• Leukodystrophy is different to multiple sclerosis – the white matter can be affected as a result of (secondary to) a number of conditions including ischaemia, infection, other metabolic conditions and multiple sclerosis.

• Physical examination
• Blood tests
• Urine tests
• MRI scans
• Nerve conduction tests
• Neurocognitive tests
• Nerve biopsy
• Genetic tests.

• Physical therapy
• Occupational therapy
• Psychological counselling
• Family counselling (including genetic counselling)
• Medications
• Dietary modifications, such as eating a strict low fat diet
• Bone marrow transplantation.

• Your doctor
• Australian Leukodystrophy Support Group Tel. (03) 9584 7070

• Leukodystrophy refers to a group of inherited disorders that affect the white matter of the brain. It causes loss of normal brain functions.
• Symptoms usually appear in early childhood.
• There is no cure, but treatment can help manage some of the symptoms.

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