Adrenoleucodystrophy
Introduction
Adrenoleucodystrophy (ALD) is a rare inherited disorder affecting the adrenal glands and ‘white matter’ of the brain, causing a progressive loss of physical and mental skills.
What is the cause?
ALD is one of a group of disorders caused by a defect of peroxisomes which are essential for the breakdown of fatty acids in cells. In ALD the gene responsible for activating the normal chemical processes is faulty which results in damaging effects on the adrenal glands, the brain cells and myelin (the substance around nerve fibres that is essential for transmission of messages between brain cells and the rest of the body).
How is it diagnosed?
When high levels of Very Long Chain Fatty Acids (VLCFAs) are found on a blood test additional tests on blood and skin cells are done to confirm the diagnosis.
Does it have any alternative name?
The condition used to be called Addison-Schilder’s Disease, after the doctor who first recognised it in 1923.
Is it inherited?
ALD is an X-linked recessive disorder which means that only boys are affected and the mother may be a carrier 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. The chromosome that determines the gender of the child will either contain ‘XX’ (female) or ‘XY’ (male).
The faulty gene in ALD is on the ‘X’ chromosome; as females have 2 ‘X’ chromosomes, the fault can be completely or partially overcome by the other healthy ‘X’ in the pair but in males, who only have 1 ‘X’, there is not another ‘X’ to provide a functioning gene. Unless there have been other affected boys in the family there may be no way of knowing who is a carrier as most carriers remain healthy; a proportion of female carriers may develop much milder neurological symptoms in adulthood. Each pregnancy carries a:-
25% chance of the child being an unaffected / non-carrier girl
25% chance of the child being an unaffected / carrier girl
25% chance of the child being an unaffected boy
25% chance of the child being an AFFECTED boy.
Is prenatal testing available?
Prenatal testing is possible by chorionic villus sampling early in pregnancy.
How common is it?
It is estimated that the incidence is approximately 1: 400,000.
How does the disease progress?
The child will probably have been well for at least the first few years of life. Between the ages of 4 years and early teens behaviour may change and memory and learning skills may cause concern; sometimes a minor infection can make the child very ill due to the problem with the adrenal glands; over the course of several months or a few years he will become increasingly unsteady, lose skills and, eventually, become more dependant than a new born baby. Vision will deteriorate and epilepsy will develop.
The condition is not a painful one and he 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; 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 will be inevitable.
Parents and carers will be aware of the child’s increasing frailty, and death is usually relatively peaceful when the time comes. The age of onset of problems, the rate of the disease progression, and the life expectancy can vary very considerably even between affected brothers but, sadly, although some boys / young men may live into mid-late teens many are likely to be in a state of unresponsiveness within a few years, or even months, of the onset of symptoms..
Is there any treatment?
Although much is known about the disease, no effective treatment is yet available to reverse the damaging process. The adrenal insufficiency can be treated by giving replacement hormones (which are essential for life) but they do not affect the underlying condition. Dietary changes (including Lorenzo’s oil) correct the VLCFA levels and probably slow down (but, sadly, not halt) the progression of symptoms if used from before or soon after symptoms develop. Every effort is made to treat the symptoms as they occur, using drugs or therapy to treat infections and epilepsy, relax muscles, and ensure a comfortable quality of life.
Specialist schooling can provide a stimulating environment and routine which is important for the child and allows his family to have some time for themselves. Though not scientifically proven, many boys gain some symptomatic relief from some of the complementary therapies such as cranial osteopathy, massage etc. In boys who are known to have the condition but in whom symptoms have not yet appeared, experimental treatment may be offered in the form of Bone-marrow Transplant; the results of this are, as yet, uncertain and the process itself is a very high risk procedure.
Is any research being done?
Much research is being done into ALD and related disorders. In the future gene therapy is likely to provide the best hope of treatment or cure but sadly this is unlikely to be soon enough to help boys already affected. Your Neurologist and Support Group can keep you informed of research progress.
Is there a Support Group?
The ALD Family Support Trust can provide information, support and contact (if wanted) with other families:
8 Morely House
320 Regent Street
London W1R 5AB
Tel: 020 7631 3336
Fax: 020 7631 3337
e-mail: [email protected]
Web: http://www.aldfst.org.uk
C.Mostyn GOSH 2005