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The commonest genetic cause of intellectual delay in boys is Fragile X Syndrome, caused by flaws on the X chromosome. But researchers are discovering there's more to this syndrome than previously thought. Even people with normal intelligence can show subtle signs. The commonest genetic cause of intellectual delay in boys is Fragile X Syndrome - caused by flaws on the X chromosome. Boys have only one X chromosome, whereas girls have a back up. But Fragile X researchers have found there's more to this condition than many imagined. For example a percentage of children with a diagnosis of autism may actually have Fragile X. Children with normal intelligence can display some signs of carrying the defect such as social anxiety, shyness and hand flapping or hand biting when excited or stressed. What's also been described more recently are problems in the maternal grandfathers. These men, who turn out to be Fragile X carriers, when they age can develop a tremor made worse when they initiate an action like handwriting. They can also have trouble with balance and memory problems. It's often misdiagnosed as Parkinson's disease or a condition like that. Another curious finding in normal intelligence adults is that mothers of children with Fragile X are at increased risk of early menopause but no-one is sure why. The reason all this is important is that it can change treatment, avoid wrong diagnoses and may help families at risk to seek genetic advice.
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