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.
I struggled to find helpful information about this condition that is parent-friendly and not overwhelming with medical speak. So I’ve cobbled together this as a way of hopefully explaining the basics of ARX but without being too confusing!
What is ARX? 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 combination Samuel has 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.
What is Lissencephaly? This literally means smooth brain and is a rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a lack of development of brain folds and grooves. It is a form of cephalic disorder. Terms such as ‘agyria’ (no gyri) or ‘pachygyria’ (broad gyri) are used to describe the appearance of the surface of the brain. Children with lissencephaly are severely neurologically impaired.
Sam also has agenesis of the corpus callosum (ACC) which is a birth defect in which the structure that connects the two hemispheres of the brain (the corpus callosum) is partially or completely absent.
Samuel’s particular form of the condition is called XLAG (an awful name, as is often the case for rare conditions).
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.
More medical blurb:
What is the normal function of the ARX gene?
The ARX gene provides instructions for producing a protein that regulates the activity of other genes. On the basis of this action, the ARX protein is called a transcription factor. The ARX gene is part of a larger family of homeobox genes, which act during early embryonic development to control the formation of many body structures. Specifically, the ARX protein is believed to be involved in the development of the pancreas, gastrointestinal tract, testes, and brain.