FRAGILE X SYNDROME Fragile X syndrome is a condition that happens when the body can’t make enough of a protein it needs for the brain to grow and develop. Fragile X can cause problems with learning and behavior. Fragile X syndrome is the most common inherited cause of learning problems and intellectual disabilities. In the United States, about 1 in 4,000 boys and 1 in 8,000 girls are born each year with fragile X. Usually, boys with fragile X have more serious learning and behavior problems than girls.What causes fragile X syndrome?Fragile X syndrome is inherited. This means it’s passed from parent to child through genes. A gene is a part of your body’s cells that stores instructions for the way your body grows and works. Genes are stored in structures called chromosomes. Everyone has 23 pairs of chromosomes, or 46 in all. For each pair, you get one chromosome from your mother and one from your father. Sometimes the instructions in genes change. This is called a gene change or a mutation. Parents can pass gene changes to their children. Sometimes a gene change can cause a gene to not work correctly. Sometimes it can cause birth defects or other health conditions. A birth defect is a health condition that is present in a baby at birth. One set of chromosomes is responsible for your gender. This set is made up of X and Y chromosomes. Girls have two X chromosomes (XX). Boys have an X and a Y chromosome (XY). Fragile X syndrome is caused when part of gene repeats more than usual on the X chromosome. Everyone has at least one X chromosome. If a girl has fragile X, her second X chromosome usually is healthy. But boys with fragile X don’t have a second healthy X chromosome. This is why symptoms of fragile X syndrome usually are more serious in boys than in girls. You can have the fragile X gene change and not have clear signs of the condition. When this happens, you’re called a carrier, and the condition is called fragile X premutation. If either you or your partner is a carrier, you can pass fragile X to your baby.You may be a permutation carrier if you have ovarian insufficiency or fragile X-associated tremor/ataxia syndrome (also called FXTAS). Ovarian insufficiency, sometimes called early menopause, is when your ovaries don’t work correctly or at all at an early age (less than 40 years). FXTAS is a condition that affects your ability to think and move. It usually affects men older than 50, but women can have it.