Gene Testing

by Kathi Prokasy

Gene testing is currently available for several different HSP genes through Athena Diagnostics, Invitae Corp and Medical Neurogenetics Lab. Together, these gene mutations cause some 55% of the dominant forms of HSP. Note: Researchers estimate there are 70 or more types of HSP. Currently, testing is not available all of them. Therefore, a "negative" result does not mean someone does not have HSP. It only means the person does not have one of these three HSP genes.

Genetic testing is a highly personal choice. People are different, and different people make different choices based on their individual circumstances and personalities. It is sometimes hard for those who choose to be tested to understand why someone would choose not to, and vice versa.Consider using the guidance of genetic counselors, mental health professionals, clergy, or other professionals to help you determine if testing is right for you.

Here are some pros and cons regarding testing.

The Case For Testing

  1. If you test positive, you have an opportunity to make informed plans. These could be childbearing choices; informing children of a test result; stimulating healthy habits regarding diet, exercise and stress reduction; and making informed decisions regarding housing and health and disability insurance. However, please remember: Some individuals do not show symptoms until very late in life, or exhibit them very mildly. Even when you test positive, there is no way to know when or how your HSP will manifest itself.

  2. You can get on with your life. While not happy to have HSP, people can develop a greater sense of clarity about the meaning of their lives. They may prioritize important things, let go of things that are trivial and insignificant, and find ways to make a contribution to others. People who test negative can have these same revelations.

  3. You can develop a support system. It can be comforting to know that you are not alone, that people care, and that other people have found ways to deal with this. Your support system can include friends, family, clergy, mental health counselors, a support group, or joining on-line support resources.

The Case Against Testing

  • If you test negative, it does not mean HSP is ruled out. Testing is currently only available for three types of HSP.

  • You can’t change the results, and you can’t go back to not-knowing the results.

  • You can still keep guessing. You won’t know when symptoms will start, or how severe they will be. HSP is quite variable, and some individuals do not show symptoms until very late in life.

  • Emotional trauma. Negative as well as positive results can be traumatic. Individuals can be need a lot of help adjusting to a positive result, and those who test negative can have difficult "survivor guilt".

  • The Risk of discrimination. If a positive report goes in your medical record or insurance forms, you can risk being discriminated against for life, health and disability insurance, jobs, etc. If an insurance company can prove that you lied about your knowledge of your test results, they can cancel your coverage.

  • Cost. The cost for the HSP-spastin gene is around $2,000. Some insurance policies will cover it, and some will not.

In vitro fertilization and fetal cell testing

Although IVF and fetal cell testing is performed routinely for other hereditary diseases, there are currently no known cases of these procedures so far being done for individuals with HSP. However, there is no reason that these procedures couldn’t be utilized for HSP patients whose families carry one of the discovered genes.

In Vitro Fertilization

Prenatal testing can be performed with in vitro fertilization, allowing an unaffected embryo to be selected for implantation in the uterus. Hormonal treatments are given to a woman so that multiple eggs ripen. These eggs are removed and fertilized in vitro.

The fertilized eggs multiply for several days, going from one cell, to two, to four, and then to eight cells. One cell is removed from the 8-cell embryo (this does not damage the embryo in any way), and genetic testing is performed to look for HSP gene mutation or for genetic markers linked with the disorder.

Unaffected embryos are implanted into the uterus and carried to term. The baby will not have HSP, and will not carry the disease.

Fetal Cell Testing

Once a woman is pregnant, fetal cells can be evaluated for genetic mutations by testing the chorionic villus, the tissue that make up the placenta. To obtain cells, a doctor withdraws a small amount of tissue from the placenta at 10 to 12 weeks of gestation by inserting a catheter into the vagina or a needle through the abdomen. If it is determined that the fetus carries an HSP gene, the parents may choose to terminate the pregnancy.


Saturday, September 8th, 2012