Finding Marfan syndrome in the womb.

Although doctors have long had the ability to flag a variety of genetic diseases before birth, they had no way of determining whether a developing fetus had inherited the defective gene for Marfan syndrome. This connective tissue disorder can severely damage the heart and arteries.

Now, for the first time, researchers have diagnosed Marfan syndrome in an affected fetus. Last year, other researchers described the genetic defect causing Marfan syndrome (SN: 7/27/91, p.55). Using that information, Natalie Vandemark of the University of Nebraska Medical Center in Omaha and her colleagues devised a prenatal test for the disorder.

In this case, a pregnant woman with a mild case of Marfan syndrome wanted to know whether her baby would also suffer the disorder. Vandemark's team took a small sample of the membrane that surrounds the developing fetus and tested it for the Marfan mutation, which runs in the mother's family. The test showed that the baby had inherited the faulty gene.

The gene codes for fibrillin, a protein that helps support blood vessels, such as the aorta, and other body structures, says Maurice Godfrey, also at the University of Nebraska Medical Center. Abnormal fibrillin leads to a weak-walled aorta, which can blow out under the increased stress that labor -- or any strenuous activity -- puts on this blood vessel.

Doctors still don't know how severely affected the child will be. In addition to cardiovascular complications, the defective gene can cause curvature of the spine and eye problems.

It's important for parents to know early that their children have this disorder, Godfrey adds. Kids with Marfan syndrome should be counseled against participating in strenuous activities, such as basketball, that can cause a weak-walled aorta to rupture and cause sudden death, Godfrey says.