(January 15, 2009 - Insidermedicine) Dr. Eric Hoffman, PhD, discusses Duchenne muscular dystrophy and its heritability. Dr. Hoffman is the Director of the Center for Genetic Medicine Research and James Clark Professor of Pediatrics at Children's National Medical Center. He is also a Professor at the School of Medicine and Health Sciences, George Washington University.
On a recent trip to Washington we caught up with Dr. Eric Hoffman who is the director of the Center of Genetic Medicine and Research and James Clark Professor of pediatrics at Children’s National Medical Center. He is also a professor at the school of Medicine and Health Sciences, George Washington University. Dr. Hoffman has over three hundred publications and is a highly cited scientist particularly for his work in the muscular dystrophies.
What is Muscular Dystrophy?
Dr. Hoffman: Muscular dystrophy is a problem of muscles and because of that is generally a problem of weakness; being able to walk or to use muscles to the point where if you’re so weak you can no longer breathe or do activities of daily living
The most common type of muscular dystrophy has been well characterized for over a hundred years, which is Duchenne Muscular Dystrophy. If you’ve seen the Jerry Lewis telethon or other fundraisers that all focus on this. So mostly this one type is the most common. And that’s due to a gene disorder, specific gene on the X chromosome that affects mostly males. The boys are fine up until kindergarten or first grade and then they just can’t keep up with their peers, they’re always the last up the stairs, they can never really break into a run in gym class and they’re brought into a physician and because it’s relatively common they’ll just do a test. The same as a heart attack they look for muscle guts in your blood which is what they do when you have chest pain see if any of your heart ends up in your blood, that means your heart has trouble. The same thing is for muscle and do the test called the Creatine Kinase Test; simple blood test.
These kids will just have huge amounts of muscle in their blood which means the muscle is actually dying. It grows back because muscle regenerates, if you walk too long or you lift too much weight you get sore, you’re sore because you’ve destroyed some muscle but it grows back and it grows back quite well.
Through cycles of this degeneration and regeneration of muscle you see a lot of evidence of that in the blood stream and unfortunately what happens with the passage of time is that the muscle has more and more trouble growing back and so they end up with muscle wasting and weakness. So they traditionally have been in a wheel chair by the age of 7 or 8 years of age and then typically succumb to respiratory failure in their mid teens.
What options are available for a child with muscular dystrophy?
Dr. Hoffman: If a child is diagnosed, usually around 3 or 4 or 5, they think that there’s a lot of things that can be done. There’s no magic bullet at this point, we’re still certainly working on therapeutic and cures but there’s lots of things that can be done, physical therapy, appropriate types of exercise, and then the other issues of everything from dealing with school systems and state aid programs. Of course now there’s lots of parent groups that are wonderful and lots of networking and a lot of interactions between the foundations, the stakeholders, the scientists and the governments. Everybody working towards the same end of helping these children so there’s certainly a lot that can and should be done if a child that is newly diagnosed and a lot of it can be quickly ascertained just through the internet
What should I do if there I a history of muscular /dystrophy in my family?
Dr. Hoffman: If there’s history in your family of muscular dystrophy, if you know of older relatives, particularly older male relatives that might of died quite young from muscle weakness, it’s quite important to go see a professional a medical geneticist or genetic counselor. Many times just by looking at your family tree they can tell you this is a problem or not for you and your future baby or risk and often times it’s not.
If it is a risk then there’s certainly genetic testing that can be done and probably should be done and again the genetic counselor and the medical geneticists co-ordinate that and so most communities are certainly medical centers now have quite active medical genetics and genetic counseling who are quite expert in this.
If one child is born with muscular dystrophy what is the risk to future children?
Dr. Hoffman: Duchenne dystrophy is actually different. It’s unique among all genetic disorders in it has a very high mutation rate again its related to the large size of the gene but it means that these cosmic rays that do exist, things that come down from space and they can hit a gene and cause a mutation just like eating too much bacon and all these things you’ve heard about nitrates.
So all these things that cause low levels of mutations in genes are going to hit the Duchenne muscular dystrophy gene a thousand times more frequently. So it has this very high spontaneous mutation rate and that translates into that families having a boy with Duchenne and actually not be at any higher risk at the next pregnancy because it really was just an egg that sustained that mutation. In other cases there are full fledged carriers and there half the sons will be affected and again genetic testing and medical genetics can discern between those.