What is ARX?

Samuel’s condition is called ARX or Aristaless Related Homeobox. Although his neurologist suspected for quite some time that he had ARX, we got the confirmed diagnosis in April 2011. As with a lot of conditions there is a spectrum, from mild to most severe cases – Sam, unfortunately, is at the most severe end. This is based I think on the severity of his seizures and that they are so hard to treat.

Samuel’s particular form of the condition is called XLAG (an awful name, as is often the case for rare conditions) which stands for x-linked lissencephaly, ambiguous genitalia, absent corpus callosum.

The ARX gene is located on the X-chromosome which is where the name of the condition comes from. All of us have 22 pairs of standard chromosomes and then a final pair that are called our sex chromosomes. Girls have two X chromosomes and boys have one X chromosome with a smaller Y chromosome. The Y chromosome only really contains genes that turn that person into a male, but the X chromosome contains many different genes performing all sorts of functions around the body. Boys are more vulnerable than girls when it comes to changes on the X chromosome, as clearly girls have two copies of all the genes present, whereas boys only have one.

Mutations within the ARX gene in themselves are rare and the phenotype of X-linked lissencephaly with ambiguous genitalia (this is the medical phrase but in Sam’s case it means he has small genitalia and his testes had not descended at birth) is rarer still.

In some genetic documentation we have read, it says that 50% die with the first year. The problem is that the professionals are basing their information on such a small number of case studies and no condition, especially ARX, is particularly ‘textbook’. There are very few case reports in medical literature and although there is a very limited life expectancy in these groups of boys on the more severe end of the spectrum, Samuel’s neurologist has said that they cannot be definitive regarding a life expectancy.

How does it affect Sam? Well Samuel has global development delay. At over a year old he is still very much a little baby and has made no development progress. He cannot support his own neck or head. He has several seizures every day and the number of these can range, depending on whether we are having a good day, from five a day to 15.

He has poor swallow co-ordination (despite swallowing his own saliva, never having needed suction and not drooling) so takes no food orally and is instead fed through a gastrostomy button on his stomach.

Find out more about ARX



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