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 made on a blood test which shows an absence / extremely low level of the enzyme ( Galactocerebrosidase).
Does it have an alternative name?
Dr Krabbe ( a Danish Neurologist) first described the condition 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?
It is estimated that the incidence in the UK is approximately 1: 100,000.
How does the disease progress?
Within the first few months, or even weeks, of life the baby will feed poorly, tend to vomit, lose weight and be excessively unsettled. From about the age of 5 months, milestones will not be achieved and, indeed, skills that have been learnt will slowly be lost again. The baby will also adopt a stiff posture and may startle very easily. The optic nerve in the brain will be affected so that vision will deteriorate and be lost over time and there may be episodes of unexplained fever. The condition itself is not painful and, obviously, the baby will be unaware of what is happening, though the effects of some of the physical problems ( ie the stiffness and startles) are likely to be upsetting and will require treatment. The brain’s control of muscles responsible for chewing, coughing swallowing etc. eventually becomes affected so that assistance with a feeding tube may be needed, and chestiness will develop which 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 9 months and 3 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 and stiffness and treat infections; 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. Though not scientifically proven, many infants gain some symptomatic relief from some of the complementary therapies such as cranial osteopathy and massage etc. In siblings who have the disease but have not yet shown any symptoms, bone-marrow transplant may be considered as an experimental treatment but does not benefit affected infants.
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 infants who already have the condition. 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:-