常见问题：脆性X染色体综合征的携带者检测
Fragile X 并发症状 is the most common cause of inherited intellectual disability. The condition affects approximately 1 in 3,600 males and 1 in 6,000 females.
Fragile X 并发症状 causes a range of symptoms, including mild to severe intellectual disability. Behavioral characteristics include 自闭症, hyperactivity, short attention span and poor eye contact.
身体特征，比如长脸, 耳朵大或突出, and flat feet – are usually more noticeable in young adults than in children and in males more than females. Males with the condition may also have enlarged testes.
Fragile X 并发症状 is caused by a change in the FMR1 gene. 的FMR1 基因位于X染色体上. This abnormal gene, which can be passed from generation to generation, is usually inherited through the gene that is carried by women.
A fragile X carrier is someone who has an altered FMR1 gene, but does not show any obvious signs 或者是脆性X染色体综合症的症状. Women who are fragile X carriers have up to a 50 percent chance 有一个患有脆性X染色体综合症的孩子. Men who are fragile X carriers will pass the altered gene to 所有的女儿都死了，但没有儿子. Daughters of carrier men are expected to be intellectually normal but are at risk of having children affected with fragile X 并发症状.
The genetics of fragile X 并发症状 are complicated. 建议进行遗传咨询 someone has a family history of fragile X 并发症状 or is shown to be a carrier of fragile X.
任何人都可能是脆性X染色体综合征的携带者. It is found among all ethnic backgrounds and racial 组. Approximately 1 in 250 women in the general population are carriers of the abnormal gene 导致脆性X染色体综合征. A woman of any age can have a child with fragile X 并发症状, 她以前是否有过孩子.
如果你有以下情况，你的风险会更大：
- 有脆性X染色体综合征的家族史
- A family history of intellectual disability, developmental delay or 自闭症 of unknown cause
- Infertility problems associated with elevated follicle stimulating hormone (FSH) levels or premature 卵巢衰竭（POF）
- A family history of adult onset ataxia and/or tremors
What is the fragile X carrier test and what do the results show?
The fragile X carrier test provides specific information about whether or not individuals are fragile X carriers, and about their risks 有一个患有脆性X染色体综合症的孩子. 测试是在一个小型的 血液样本. 结果通常在两周内得到. 测试提供更准确的结果 99%的情况下. Other causes of intellectual or developmental disability are not identified through this test.
What are the possible results from a fragile X carrier test?
There are four possible results from a fragile X carrier test:
- 负. You are not a carrier for the most common alteration in the FMR1 gene and your baby is not at increased risk for fragile X 并发症状.
- 中间. Your results fall in the range between negative and premutation. Your baby is not at increased risk for fragile X 并发症状. Future generations may be at risk for fragile X 并发症状.
- 前突变. 你是变异FMR1基因的携带者. 你可能有提前绝经的风险. 你的宝宝有患脆性X染色体综合征的风险. 产前诊断测试是可用的.
- 完整的突变. 你是变异FMR1基因的携带者. 你的宝宝有患脆性X染色体的危险 并发症状. 产前诊断测试是可用的.
Genetic counseling is recommended and available when someone is shown to be a carrier of fragile X.
产前检查可由以下人员进行 羊膜穿刺术 16到20周左右 绒毛膜绒毛取样 at 10 to 13 weeks to determine if a fetus has inherited the fragile X gene.
For more information about fragile X 并发症状, genetic counseling, or to arrange 运营商测试，请联系 产前诊断中心.
加州大学旧金山分校健康 medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.
