Cardiac disease, particularly dilated cardiomyopathy and heart failure, is the major cause of mortality in patients with muscular dystrophy and is present in most boys with Duchenne muscular dystrophy and approximately 70 percent of those with Becker muscular dystrophy. These are the two common forms of muscular dystrophy caused by defects in a gene called dystrophin.
"It should be the standard of care for all newly diagnosed Duchenne and Becker muscular dystrophy patients to be referred to a cardiologist for screening, probably by 10 years of age or earlier," says Dr. Jeffrey A. Towbin, professor of pediatrics at BCM and chief of pediatric cardiology at Texas Children's Hospital.
Towbin and his group studied 69 boys with DMD and BMD. After the first abnormal echocardiogram, which occurred at 14-15 years, 31 boys were started on ACE inhibitor or beta blocker therapy. During the follow-up two patients remained stable with their dilated cardiomyopathy, eight showed improvement and 19 normalized both heart size and function.
"This study also helped us realize that while some dystrophin-gene mutations are predictors of early onset cardiac abnormalities, others may actually protect against early development of these abnormalities," says Towbin.
Cardiac symptoms typically appear late in the course of cardiomyopathy, in part because affected individuals are usually wheelchairchair bound and often physically inactive. Heart disease progresses quickly, leading to premature death, often before 25 years of age.
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"This work provides new insights into the mechanisms that underlie biodiversity," Albertson said. "Moreover, our results show interesting parallels with recent work in another evolutionary model, Galapagos finches." In both studies bmp4 is implicated as underlying adaptive variation in jaw shape. Higher levels of bmp4 result in thicker jaws, whereas lower levels are associated with thinner jaws. The fact that bmp4 may underlie morphological diversity in both birds and fishes, raises the interesting possibility that it might play a broader role in vertebrate evolution."
"Superficial similarities between these two systems may be similar on a molecular level," Albertson adds. "This research is exciting on several levels. We now have the opportunity to explore what genes make a head, and which genes create variations in head shape. Furthermore, this work will help us gain a better understanding of, and offer possibilities for preserving biodiversity of species."
R. Craig Albertson is a Staff Associate and a member of the laboratory of Pamela C. Yelick, Ph.D. in The Forsyth Institute Department of Cytokine Biology. His work is supported through a National Institute of Health training grant awarded to the Forsyth Institute.
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