Krabbe’s Leucodystrophy is a rare inherited disorder affecting mainly the ‘white matter’ of the brain, causing a progressive loss of physical and mental skills.
What is the cause?
Krabbe’s Disease is one of a group of Leucodystrophies caused by an abnormal build-up of substances, ( Cerebrosides) 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 ( Beta-galactocerebrosidase) but, in Krabbe’s Disease, 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 confirmed on a blood test which shows a low level of the enzyme (Galactocerebrosidase).
Does it have an alternative name?
Dr Krabbe ( a Danish Neurologist) first described the Infantile form of the condition ( affecting babies) in 1916; it is also known as Globoid Body / Globoid Cell Leucodystrophy, describing the appearances of the affected cells in the white matter of the brain.
Is it inherited?
Krabbe’s Disease 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 Krabbe’s Disease ( 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 possible in some cases by chorionic villus sampling early in pregnancy following DNA testing of the parents and the affected sibling.
How common is it?
The incidence of the Infantile form of Krabbe’s Disease is estimated to be approximately 1: 100.000: the late onset form is considerably less common.
How does the disease progress?
The late onset form of Krabbe’s disease is very rare and can vary very considerably between different affected people, both in the way in which the symptoms appear and the rate at which the condition progresses. From early childhood the child will not achieve expected milestones of motor development; physical skills will be increasingly impaired and, probably after many years, memory will become poor and there will be a slow progressive loss of mental skills; the optic nerve in the brain will be affected so that vision will deteriorate and may be lost over time; in some cases there are long periods ( years) of relative stability but eventually from late childhood or early adulthood the disease will have caused both physical and mental deterioration which will cause the young person to be totally dependant; the child will notice the increasing physical difficulties but will probably be less aware of the intellectual deterioration, and the condition is not a painful one. The brain’s control of the muscles responsible for chewing, coughing and 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; death may occur in late childhood or later into adulthood, the time span varying greatly between affected people, but parents and carers will be aware of the 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 and stiffness and feeding can be assisted. Parents will be advised on maintaining mobility as long as possible, and on seating and limb excercises to maintain comfort. Though not scientifically proven, many children gain some symptomatic relief from some of the complementary therapies such as cranial osteopathy and massage etc. In very mildly affected children bone-marrow transplant may be considered as an experimental treatment.
Is any research being done?
Research is progressing rapidly with increasing understanding of the genes and how they work; treatment is obviously the goal but sadly, as yet, research has not yet led to the ability to stop the effects of the disease. 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 Krabbe’s Disease, can provide written information, telephone advice, support and contact (if wanted) with other families:-