Despite Progress, Cure for Sickle Cell Disease Remains Elusive
(HealthDay News) -- Sickle cell anemia can literally drain the life out of person, but many more people are surviving this debilitating disease into middle age.
The most common inherited blood disease in the United States, sickle cell disease affects about 80,000 Americans, primarily blacks. Another 2 million Americans have the defective gene that causes the disorder, making them potential carriers.
Thanks to improvements in diagnosis, treatment and research, half of those with the condition are now more than 50 years old. Until recently, people with sickle cell rarely survived childhood, according to the National Human Genome Research Institute.
"I have had five adult patients, one more than 60 years old, who watch out for themselves. They have been good, cooperative patients who make sure they optimize their care," says Dr. Kenneth Algazy, a clinical professor of medicine at the University of Pennsylvania School of Medicine.
Sickle cell anemia is caused by the production of faulty hemoglobin, a key component of red blood cells. Hemoglobin carries oxygen from the heart to all parts of the body.
Once the hemoglobin molecules have released their oxygen, some can cluster to form long, rod-like structures. These rods cause the red blood cells to stiffen and to take on a sickle shape, preventing them from slipping through small blood vessels.
The resulting clots and blockages inhibit the flow of oxygen to the body's tissues and organs, particularly the lungs, kidneys and brain. The oxygen deprivation causes severe and potentially fatal complications, including stroke, Algazy says.
For the very few patients who have a sibling without sickle cell who are a genetically compatible match, a possible cure lies in a bone marrow transplant. The donor's healthy marrow lets the patient produce his own healthy hemoglobin, Algazy says.
"But that's very rare. Essentially, there is no cure," he says.
So researchers are turning to genetics. They’re trying to correct the defective gene that causes sickle cell and insert it into the bone marrow of victims, to stimulate the production of normal hemoglobin.
Scientists at Harvard Medical School and the Massachusetts Institute of Technology reported in 2001 that they had corrected sickle cell disease in mice using gene therapy, according to the Human Genome Research Institute.
However, such a cure is years away for human victims.
"In five or 10 years there may be hope for a cure," Algazy says.
Other areas of hope are drugs that increase the level of fetal hemoglobin in the blood. Fetal hemoglobin, found in fetuses and infants, stops the red blood cells from changing shape and helps ease the intense pain often suffered by patients.
Currently, hydroxyurea, which is also used to fight certain cancers, is the only drug approved for this use. However, researchers at the University of Illinois in Chicago have studied another drug, called decitabine. In a preliminary study this drug increased the levels of fetal hemoglobin in all eight patients who took it on a daily basis for nine months. Decitabine is also being tested to combat certain cancers that attack the blood.
None of the patients had found relief using hydroxyurea, says study author Joseph DeSimone, a professor of medicine at the university. With decitabine, all found their fetal hemoglobin levels rose approximately 11 percent to 14 percent.
A level approaching 20 percent is needed to reduce the symptoms of the disease, which can include intense pain as body parts are deprived of oxygen, he says.
"It worked well in terms of increasing fetal hemoglobin," DeSimone says, "and there was less red cell adhesion and less clotting."
Also encouraging was the absence of immediate side effects such as nausea, infection around the site of the injection, or rashes. The last is a common side effect of hydroxyurea, DeSimone says. Further studies are underway.
"Sickle cell anemia is a lousy disease and can be very painful, and there are good things that are possible so people can go back to work and feel better," DeSimone says.
On the Web
To learn more about sickle cell disease, visit the American Sickle Cell Anemia Association.
SOURCES: Joseph DeSimone, Ph.D., Associate Chief of Staff of Research, the Jesse Brown Veterans Affairs Medical Center-West Side and Director of Sickle Cell at University of Illinois at Chicago; Kenneth Algazy, M.D., clinical professor of medicine, hematology/oncology division, University of Pennsylvania, Philadelphia and Medical Director, Center for Lung Cancer and Related Disorders; Section Chief Hematology/Oncology, VA Medical Center, Philadelphia
Publication date: December 26, 2005
Author: Janice Billingsley, HealthDay Reporter
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