What is fragile X syndrome?
Fragile X syndrome is the most common form of inherited mental retardation in males and is also a significant cause of mental retardation in females.
It affects about 1 in 4,000 males and 1 in 8,000 females and occurs in all racial and ethnic groups. If you should know, my son also have it.
Nearly all cases of fragile X syndrome are caused by an alteration (mutation) in the FMR1 gene where a DNA segment, known as the CGG triplet repeat, is expanded. Normally, this DNA segment is repeated from 5 to about 40 times. In people with fragile X syndrome, however, the CGG segment is repeated more than 200 times.
The abnormally expanded CGG segment inactivates (silences) the FMR1 gene, which prevents the gene from producing a protein called fragile X mental retardation protein. Loss of this protein leads to the signs and symptoms of fragile X syndrome. Both boys and girls can be affected, but because boys have only one X chromosome, a single fragile X is likely to affect them more severely.
What are the symptoms of fragile X syndrome?
A boy who has the full FMR1 mutation has fragile X syndrome and will have moderate mental retardation. They have a particular facial appearance, characterized by a large head size, a long face, prominent forehead and chin and protruding ears. In addition males who have fragile X syndrome have loose joints (joint laxity), and large testes (after puberty).
Affected boys may have behavioural problems such as hyperactivity, hand flapping, hand biting, temper tantrums and autism. Other behaviours in boys after they have reached puberty include poor eye contact, perseverative speech, problems in impulse control and distractibility. Physical problems that have been seen include eye, orthopaedic, heart and skin problems.
Girls who have the full FMR1 mutation have mild mental retardation.
Family members who have fewer repeats in the FMR1 gene may not have mental retardation, but may have other problems. Women with less severe changes may have premature menopause or difficulty becoming pregnant.
Both men and women may have problems with tremors and poor coordination.
How is fragile X syndrome diagnosed?
There are very few outward signs of fragile X syndrome in babies, but one is a tendency to have a large head circumference. An experienced geneticist may note subtle differences in facial characteristics. Mental retardation is the hallmark of this condition and, in females, this may be the only sign of the problem.
A specific genetic test (polymerase chain reaction [PCR]) can now be performed to diagnose fragile X syndrome. This test looks for an expanded mutation (called a triplet repeat) in the FMR1 gene.
Is fragile X syndrome inherited?
This condition is inherited in an X-linked dominant pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. The inheritance is dominant if one copy of the altered gene in each cell is sufficient to cause the condition.
In most cases, males experience more severe symptoms of the disorder than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
I treat our circumstance as a challenge
Well, I for one have my son diagnosed with fragile X syndrome and it is not easy as I may usually sound it is but me and my husband are doing our best. We keep on the challenge!