October 28, 1998
"For the first time, a test allows us to exclude carrier status with certainty....We lift a weight from thousands of women."
Scientists now can predict, with 99 percent accuracy, carriers of the gene for adrenoleukodystrophy (ALD), the disease featured in the movie "Lorenzo's Oil." Unlike existing tests that depend on changes in blood chemistry, the new procedure developed at Johns Hopkins -- DNA carrier-based testing -- directly analyzes a woman's genes for specific mutations.
"Because of this test, women who've delayed having children because of uncertainty about passing on the disease can have a new confidence," says geneticist Garry R. Cutting, M.D., one of the researchers and head of Hopkins' DNA Diagnostic Laboratory. The scientists present the technique this week at The American Society of Human Genetics meetings in Denver.
ALD is an inherited disorder that, in its most devastating form, causes death of the brain's "white matter" -- nerve cells that transport information within the brain and from brain to spinal cord. The adrenal glands also are destroyed. Boys with ALD appear healthy and normal until early childhood, when they begin to regress mentally. Thinking deteriorates, along with the ability to move or see. The severe form, which affects about 40 percent of all male ALD patients, kills most children by age 10. "Families are severely traumatized by this downhill path," says neurologist Hugo W. Moser, M.D., also on the Hopkins research team.
ALD results from an altered recessive gene carried on the X chromosome, one of the sex chromosomes. Other "sex-linked" diseases include Duchenne muscular dystrophy and hemophilia. If a male inherits the one of his mother's two X chromosomes that bears the altered gene, he's likely to get the disorder. Most women who have the gene are unaware that they're carriers.