What is the 11,22 translocation?

Information from: http://www.emanuelsyndrome.org/1122trans.htm

There are many different types of translocations, however the t(11;22) is known as a reciprocal translocation and is the most common recurring reciprocal translocation seen in humans. A reciprocal translocation means that there is a two way exchange of information between these two chromosomes. Nothing is missing and nothing is extra, thus making a carrier of this translocation “balanced” in terms of genetic information. Translocations are a relatively common occurrence (1 in 500 people are estimated to have one) and there is nothing you did to make it happen. Translocations can occur between any chromosomes.  It happens in unrelated families, from various ethnic backgrounds. It can be found going back several generations in some families. It also has been found, rarely,  to happen spontaneously in some carriers.

How did it happen in the first place? Many generations back, likely in a male relative’s sperm, chromosomes 11 and 22 switched q arms. These two chromosomes have something in common; they both have PATRRs in their DNA sequence, which makes them prone to breakage in that area. If a chromosome breaks, it often latches on to another broken chromosome end nearby. The two ends fuse together and become a new chromosome – which we call a “derivative.” The derivative chromosome can be passed on to future offspring, and it can also cause problems with how chromosomes segregate – that is, how they are divided up during the process of making eggs and sperm. This is why some balanced translocation carriers have trouble conceiving a pregnancy, and how you can end up with a pregnancy in which the baby has an unbalanced karyotype.

If you are a female carrier of the t(11;22):

• you have an approximately 5-6% chance of having a child with Emanuel Syndrome for each pregnancy conceived
• you have an approximately 55% chance of having a child who carries the balanced translocation for each pregnancy conceived
• you have a 23-37% chance of having a miscarriage for each pregnancy conceived

If you are a male carrier of the t(11;22):

• you have an approximately 2-5% chance of having a child with Emanuel Syndrome for each pregnancy conceived
• you have an approximately 40% chance of having a child who carries the balanced translocation for each pregnancy conceived
• you have a 23-37% chance of your partner having a miscarriage for each pregnancy conceived.

There are t(11;22) carriers in our group who have had more than one natural child born with Emanuel Syndrome. We also know of a few pregnancies that resulted in the birth of twins both affected by Emanuel Syndrome, and one family who has twins where only one of the children was affected with Emanuel Syndrome.

Most often, in about 90% of the cases of Emanuel Syndrome, it is determined that the mother is the carrier of the balanced t(11;22). Carriers will have some eggs/sperm that will be completely normal – ie – not affected by either the balanced translocation or have the extra marker chromosome present, but some of the eggs/sperm will contain the extra chromosome that results in Emanuel Syndrome. It is theorized that, for parents of a child with ES, women are more frequently found to be the carrier because sperm carrying the extra chromosome may be less able to fertilize an egg than normal sperm. However, women’s eggs, no matter if they carry the extra chromosome or not, seem to have equal chances of being fertilized.

Many members in our group who carry the t(11;22) have had experience with multiple miscarriages, periods of infertility, and some know what it is like to lose a child.

Carriers of the balanced t(11;22) are considered expected to be to be normal in every respect, except for the challenges they can face when trying to have a baby.