Late Infantile Form
Metachromatic Leucodystrophy is a rare inherited disorder affecting mainly the ‘white matter’ of the brain, causing a progressive loss of physical and, later, mental skills.
What is the cause?
Metachromatic Leucodystrophy is one of a group of Leucodystrophies caused by an abnormal build-up of substances, (metachromatic material: Sulphatides) in the nerve cells, particularly in the white matter of the brain, which take the place of Myelin, the insulating material which is essential for normal transmission of messages between nerves. These substances are normally broken down and removed from the body by an enzyme (Arylsulphatase A) but, in MLD, the gene responsible for producing the enzyme is faulty so the normal process cannot occur. As the brain is the control centre of the whole body, blockages in the messages to other parts of the body will prevent those parts working efficiently, even though the parts themselves seem quite healthy.
How is it diagnosed?
The diagnosis is made on urine tests which show the metachromatic material (Sulphatides) and on a blood test which shows an absence of the enzyme (Arylsulphatase A)
Does it have any alternative name?
MLD is sometimes known by its medical description: Sulphatide Lipidosis or Sulphatidosis and the Late Infantile Form may also be called Greenfield’s Disease.
Is it inherited?
MLD is an autosomal recessive disorder; this means that both parents are carriers of the disease. Human beings have about 30-40,000 different genes, each of which has a function in making an individual person. The genes are arranged in pairs (1 of the pair from each parent) on 23 chromosomes. Inevitably, some of these genes are faulty; a normal gene can overcome a faulty one, but if both genes in the pair are faulty, the genetic instructions cannot work. Most people carry different faulty genes but in MLD (and other recessive conditions) parents, though healthy themselves, carry the same faulty genes, and risk passing them on to their children.
Each pregnancy carries a 25% chance of the child being affected
a 75% chance of the child NOT being affected.
Is prenatal testing available?
Prenatal testing is usually possible by chorionic villus sampling early in pregnancy.
How common is it?
It is estimated that the incidence in the UK is approximately 1: 40,000.
How does the disease progress?
In the Late Infantile Form of MLD the infant’s development starts to slow down between the ages of 6 months and 2 years; he/she may become rather unsettled and appear physically floppy (hypotonic); over the following months motor skills will not progress as expected, and, indeed skills that have been learnt will be lost. Over the course of the next few years the child becomes as dependent as a new- born baby again, usually developing stiffness of the legs ( spasticity) and eventually loses all understanding or real awareness of his/her surroundings; very rarely epileptic seizures may develop. The condition is not a painful one and the child will be unaware of what is happening in the later stages of the disease. The brain’s control of the muscles responsible for chewing, coughing, swallowing etc. eventually becomes affected so that assistance with a feeding tube may be needed, and chestiness will develop and may lead to infections and increasing physical weakness. Eventually the combination of the diseased brain and physical weakness becomes too great to sustain life, and death usually occurs between the ages of 5- 8 years. Parents and carers will be aware of the child’s increasing frailty, and death is usually relatively peaceful and expected when the time comes.
Is there any treatment?
Although there is no treatment yet available that can stop the disease, every effort is made to treat the symptoms as they occur. Thus drugs can be given to relieve muscle spasms, treat infections and try to control seizures (should they occur); pain relief and sedative drugs can be given if required, and feeding can be assisted. Physiotherapists and others can advise parents on positioning, seating and exercising the limbs to maintain comfort. Specialist schooling will be required and it is important for the child to have this stimulating environment and social contact and, indeed, for the parents to have some time for themselves and other family members and friends. Though not scientifically proven, many children gain some symptomatic relief from some of the complementary therapies such as cranial osteopathy and massage etc
Is any research being done?
Research is progressing in various areas concerning Leucodystrophies and other progressive neurological disorders, particularly ‘mapping’ genes and understanding which gene is responsible for what process. Sadly, however, any treatment that could reverse the disease process is unlikely to be discovered quickly enough to help children who already have symptoms. Your neurologist and information available from the support group can keep you informed of research progress.
Is there a Support Group?
The Research Trust for Metabolic Diseases in Children: CLIMB, which includes the Leucodystrophies, can provide written information, telephone advice, support and contact (if wanted) with other families
Climb National Information and Advice Centre for Metabolic Diseases
176 Nantwich Road
Tel : 0800 652 3181<br>
e-mail : email@example.com
Fax : 0870 770 0327
Web : http://www.climb.org.uk