April 9 (HealthDay News) -- The same 10 gene mutations responsible for cardiac hypertrophy (thickening of the heart muscle) in adults are also associated with many cases of this rare but life-threatening condition in children, says a U.S. study.

The mutations even showed up in children who had no family history of the condition, the researchers noted.

Currently, little is known about the causes of cardiac hypertrophy in children, so no diagnostic tests for children have been developed. The findings of this study suggest that the same genetic test designed for adults can be used in children, which may help increase knowledge about the condition and lead to new kinds of treatments, said study authors Christine and Jonathan Seidman, professors at Harvard Medical School in Boston.

About one in 100,000 children develops cardiac hypertrophy, which can lead to sudden death. About 3 percent to 4 percent of adults have the condition. Most of the genes implicated in cardiac hypertrophy encode sarcomere proteins, which help the heart tighten and relax to pump blood.

"Cardiac hypertrophy increases your risk of all types of negative cardiovascular outcomes, including heart failure and sudden death. Although the condition is rare in children, the prognosis is even worse. Kids with cardiac hypertrophy are often candidates for transplantation," Jonathan Seidman said in a prepared statement.

"Labs have done work on the genetic underpinnings of cardiac hypertrophy in adults, but few thought that the research applied to children. For years, doctors assumed the two conditions were clinically distinct," Christine Seidman, who is also a member of the HMS-Partners HealthCare Center for Genetics and Genomics, said in a prepared statement.

In this study, the Seidmans and their colleagues from Children's Hospital Boston and Baylor College of Medicine analyzed DNA from 84 children diagnosed with cardiac hypertrophy before age 15. Of those, only 33 had family histories of the condition.

The researchers identified mutations in the 10 suspect genes in 25 of the 51 children without family histories of cardiac hypertrophy and in 21 of the 33 with family histories.

"I think it's remarkable that we found mutations in nearly 50 percent of the kids who don't have family histories," Christine Seidman said.

The researchers also analyzed DNA from 11 pairs of parents and found that in seven of those couples, one parent had the same mutation as his or her child. The parents with these mutations believed their hearts were healthy, but echocardiograms revealed thickening of the muscle in some cases.

"We still don't know why the children presented symptoms so much earlier than their parents. We suspect that other genes must influence the disease presentation," Jonathan Seidman said.

Further genetic testing of children with cardiac hypertrophy and their parents may explain this and help doctors select appropriate treatments, the researchers said.

The study was published online April 9 in the New England Journal of Medicine.

SOURCE: Harvard Medical School, news release, April 9, 2008