Genetic Ataxias are inherited. There are mainly two forms of inherited Ataxias. These are known as Recessive and Dominant.
Recessive Ataxia usually has an onset in childhood. Though there may be no family history of such a disorder, it will occur if both parents are carriers of the defective gene. Usually the parents will be totally unaware of this fact until one of their children shows signs of balance and co-ordination problems – usually after the age of six years. Each parent has two copies of every gene and for those with one defective gene each there is a one in four chance, with every pregnancy, that the child will inherit the defective gene from each parent. In such cases the child will develop a Genetic Ataxia.
If you have a relative who has been diagnosed with an ataxia and would like to be tested to see if you are a carrier, a referral letter would need to be sent by your GP to:
Professor Andrew Green, Director of the National Centre for Medical Genetics
Our Lady’s Hospital for Sick Children, Crumlin, Dublin 12.
Dominant Ataxia occurs when a faulty gene, in one parent only, causes the abnormality. In this instance the normal gene does not compensate for the abnormality. There is a 50% chance that the child will inherit the abnormal gene from the parent and thus develop the Ataxia. There is also a 50% chance the child will inherit the good gene and therefore, will not be affected and will not pass the bad gene on to the next generation. Usually the onset of Dominant Ataxia’s occur in later life. There are several other Ataxia’s, such a Cerebellar Ataxia which usually occur in adult life but the symptoms are very similar to those for the other Ataxia’s.