常见问题:脊髓性肌萎缩症的携带者测试
Spinal muscular atrophy (SMA) is a genetic disease that results in progressive muscle weakness and paralysis. The condition occurs in 1 in 10,000 live births and affects both males and females.
SMA有三种类型. The most severe type is usually diagnosed within the first few months of life. Affected children have severe muscle weakness and typically do not survive past the age of 2.
另外两种类型的SMA, 哪些比严重型更不常见, 轻微的肌肉无力. Most affected individuals need to use wheelchairs or need assistance with walking. Life expectancy for the less severe types ranges from the teenage years to adulthood. Those with the mildest form of SMA are expected to have a normal lifespan.
目前还没有治愈SMA的方法. Medical treatments for the milder forms of SMA may help extend the expected lifespan in some cases. The great majority of babies with the most severe form of SMA do not survive past 2 years of age.
SMA是一种遗传性疾病. Our genes come in pairs, with one copy inherited from each parent. Some genes have mutations in them, and do not function properly. 拥有一个无功能基因副本的人是携带者.
Carriers for SMA have no symptoms, but can pass the non-functioning gene on to their children. An individual must inherit two non-functioning SMA genes – one from each parent – to have symptoms of SMA.
If both parents are carriers there is a one in four (25 percent) chance that both will pass on the non-functioning gene, which would result in a pregnancy affected with spinal muscular atrophy.
Who should consider carrier testing for spinal muscular atrophy?
Those who have a family member with SMA or a family member known to be a carrier are at increased risk to be a carrier themselves. Genetic counseling is recommended in these cases to determine the likelihood of having a pregnancy or child affected with SMA.
An individual without a family history of SMA can be a carrier for this condition as well. 大约50人中有1人, 无论种族背景如何, 是否携带导致SMA的异常基因.
携带者检测可以通过简单的血液检测. The test can detect the most common mutation that is associated with SMA and will detect approximately 90 percent of carriers. A negative carrier test will greatly reduce the likelihood of having a child affected with this condition.
There are gene changes (mutations) associated with SMA that are not included in the carrier test. 除了, in a small number of cases where a child is found to be affected, 只有一个父母是携带者. 出于这两个原因, a negative carrier test cannot eliminate the possibility of having an affected child.
What does it mean if I am a carrier for spinal muscular atrophy?
If you are found to be a carrier for SMA, your partner should undergo carrier testing as well. If your partner's test is negative, the chance to have an affected child is low. 如果你的伴侣也被发现是SMA携带者, 有四分之一(25%)的几率会导致受影响的怀孕.
If two parents with no family history of SMA are found to be carriers with routine screening, it is not possible to predict whether they are at risk of having children with the severe form of SMA or one of the less severe forms of SMA.
是的. If both partners are carriers of SMA, prenatal testing is available. 绒毛膜绒毛取样 10到14周 羊膜穿刺术 at 16 to 20 weeks can be performed to determine if the fetus has inherited two copies of the SMA gene mutation. If both partners are carriers and you are thinking of becoming pregnant, 还有其他选择. 你可以和遗传咨询师讨论这些问题.
了解更多关于脊髓性肌萎缩症的信息, 遗传咨询或安排携带者或产前检测, 联系 UCSF产前诊断中心 at (415) 476-4080.
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.