A lesson in Genetics...

Today from the Genetic Counselors at OHSU called. The results of Ben's genetic testing had arrived.

Ben was tested for an autosomal recessive disorder called Pendred Syndrome. Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop. A mutation in a gene on one of the first 22 nonsex chromosomes can lead to an autosomal disorder.

Genes come in pairs. Recessive inheritance means both genes in a pair must be defective to cause disease. People with only one defective gene in the pair are considered carriers. However, they can pass the abnormal gene to their children.To have an autosomal recessive disorder two copies of the gene must be mutated for a person to be affected. One copy comes from the mother and the other from the father. The parents are usually unaffected and unknowingly each carry a single copy of the mutated gene (and are referred to as carriers).




If both parents are carriers, there is a 25% chance of a child inheriting both abnormal genes and, consequently, developing the disease or syndrome. There is a 50% chance of a child inheriting only one abnormal gene and of being a carrier, like the parents, and there is a 25% chance of the child inheriting both normal genes.

The results from Ben's tests show he has two mutated genes, what is expected with someone affected by an autosomal recessive disorder. One of the mutations is to a gene known as SLC26A4 on chromosome 7, which causes Pendred Syndrome. The other is a mutation that has not been seen before. The results stated the exact mutation is unclear.

Because Pendred syndrome is a recessive trait, a child needs to inherit two mutated SLC26A4 genes—one from each parent—to have Pendred syndrome. This means Ben's diagnosis is still a bit unclear. To determine if Ben truly has Pendred's both parents need to be tested to see if we are carries of the mutated gene. If we are carries, it is possible Ben has Pendred's with a mutation that has not yet been documented. Lucky Ben!

It is important to us to determine whether or not Ben has Pendred's because it can cause some other complications for him as he grows older. Mostly, we will need to monitor his thyroid as he enters puberty. He may also develop some balance issues as he begins to try to walk.

All in all, the answer is good for Ben and good for us. It's a bit strange, in a way, to think that people can carry this mutated gene around unknowingly. If they have a child, that child may or may not be affected. It may never surface. But then again, it just might. Lucky, lucky Ben!