The rare disorder is Liddle syndrome, first reported in 1963 in a 15-year-old Alabama girl diagnosed with a blood pressure of 180/110 mmHg, says Dr. Yanbin Dong, molecular geneticist and cardiologist at the Medical College of Georgia.
Interestingly, an inexpensive diuretic worked best to manage her problem. Tests years later found the reason was that genes involved in the channel that recycles sodium from food into the body were drastically mutated. "This mutation enables sodium to come back into the body like a flood," says Dr. Dong.
Today he is looking at sodium channel genes implicated in Liddle syndrome to identify less severe changes that could be used to screen for hypertension risk in the general population.
"My hypothesis is if Liddle syndrome is caused by these nasty, drastic mutations, maybe the majority of hypertension can be caused by milder, less nasty polymorphisms or variations in the same genes," says Dr. Dong who received a $1.43 million grant from the National Heart, Lung and Blood Institute to see if he is correct.
He's recruiting 300 healthy blacks ages 15 to 19 with normal blood pressure to a Georgia Prevention Institute study that first measures sodium-handling following environmental stress, then analyzes the genes of those who don't handle it well.
Dr. Dong is exploring findings by Dr. Gregory A. Harshfield, director of the Georgia Prevention Institute, showing that some healthy youths, particularly black youths, continue to retain sodium after the stress that drove up their blood pressure is gone. This impaired stress-induced pressure natriuresis occurs in about 36 percent of healthy black youths and 25 percent of healthy white youths, according to Dr. Harshfield's studies.