Hi Dina Autosomal dominant - Autosomal means that both males and females are affected. Dominant means that each child of an affected individual (only ONE parent needs to pass on the gene) has a 50% chance of inheriting the genetic change that causes ataxia. The dominant Ataxias are labeled ‘Spinocerebellar Ataxias (SCAs) and are numbered in order of their discovery ( SCA1 was the first, and as of 2017 SCA43 was the most recent, but since then I recall people mentioning other recent discoveries.
Autosomal Recessive - Autosomal, again this means that both males and females can be affected. Recessive means that in order to have the disease, a person must inherit a genetic change (mutation) from BOTH of their parents. This form of ataxia is labeled SCAR followed by a number. If a child inherits a mutant gene from both parents, they will go on to have ataxia. But if they inherit just one of the genes, they will be a ‘carrier’ and therefore unaffected. However, if they as carriers go on to have children with someone else who is a carrier, it’s possible the children will be affected. Inheritance in this form could go on for decades until two carriers come together, and the disease manifests.
And there are other recognised patterns linked with inheritance.
Genetic tests can be very difficult to interpret. Therefore, it is important to do genetic testing in consultation with a health care provider who is familiar with how to interpret genetic testing results. Diagnostic testing is usually done in situations where a patient has symptoms of ataxia, and the testing is done to try and find out the precise genetic cause. In some cases, diagnostic testing will find out a specific cause for the ataxia, while in other cases, it may not find out the cause. If the results of diagnostic testing are normal, this does not mean the diagnosis of ataxia is wrong. It just means that the specific cause couldn’t be identified using current technology. A few years ago, at a Convention, there was a report saying that to date almost 100 SCAs had been identified, with even more expected. But, many of them are still waiting for a test to be devised for patients.
Whole Genome/Whole Exome Sequencing - In the past, each ataxia has had to be methodically tested one at a time. Genetic testing options are now available that can test for hundreds ( or even thousands) of genes at the same time. Such testing may be an option if a genetic cause is suspected, but traditional genetic testing has not been able to identify the cause of ataxia in a patient. Whole Genome Sequencing looks at all of the DNA in your body. In contrast, Whole Exome Sequencing focuses on a small part of the Genome that encodes our genes. Most of the mutations that are known to cause ataxia lie within the smaller Exome Sequence. Currently, Whole Exome Sequencing is available at many clinical laboratories, while Whole Genome Sequencing is very limited.
Laboratories use a technology called Next Generation Sequencing when performing such specific tests. Older Sequencing technologies were very costly and labor intensive. Next Generation Sequencing is a new way of doing genetic testing that allows scientists to look at large numbers of genes in a cost effective way.
I hope this explanation has helped xB