Sickle Cell Anemia Health Article

Gene research

Replacing the gene that produces the defective hemoglobin in sickle cell disease patients with one that makes normal hemoglobin may be a possible treatment due to recent research. According to a 1998 report in Science, researchers studied the blood cells from people who carry the sickle cell gene. By using an enzyme called a ribosome, the study was able to alter sickle cells into normal cells. The ribosome cut out the mutated instructions in the cells' genetic pattern and replaced them with the correct instructions. Researchers hope that this gene therapy will allow the cells to make normal hemoglobin—leading to the ultimate treatment for those with sickle cell disease.

In late 2001 genetic scientists reported that they had designed a gene that might lead to a future treatment of sickle cell anemia. Although the gene had not tested in humans, early results showed that the injected gene protected cells from sickling. As of 2003, experiments in gene therapy for sickle cell disease have been carried out in mice, using lentiviral vectors to transfer the corrective gene into the mouse's stem cells. This technique, however, has not yet been attempted in human subjects as of late 2003.

Expected results

Several factors aside from genetic inheritance determine the prognosis for affected individuals. Therefore, predicting the course of the disorder based solely on genes is not possible. In general, given proper medical care, persons with sickle cell anemia are in fairly good health most of the time. The life expectancy for these individuals has steadily increased over the last 30 years, and many are now surviving past the age of 50. In the United States, the average life expectancy for men with sickle cell anemia is 42 years; for women, it is 48 years. The most common causes of death are infections, lung disease, the blocking of a blood vessel supplying a vital organ, and kidney failure. Pregnant women with sickle cell disease are particularly vulnerable to infection, most often pneumonia or urinary tract infections.

Prevention

The sickle cell trait is a genetically linked, inherited condition. Inheritance cannot be prevented but may be predicted. Screening is recommended for individuals in high-risk populations; in the United States, African Americans, and Hispanic Americans have the highest risk of being carriers.

Screening at birth offers the opportunity for early intervention; more than 40 states include sickle cell screening as part of the usual battery of blood tests done for newborns. Pregnant women and couples planning to have children may also wish to be screened to determine their carrier status. Carriers have a 50% chance of passing the trait to their offspring. Children born to two carriers have a 25% chance of inheriting the trait from both parents and having sickle cell anemia. Carriers may consider genetic counseling to assess any risks to their offspring. The sickle cell trait can also be identified through prenatal testing, specifically through use of amniotic fluid testing or chorionic villus sampling.

By maintaining a good diet, staying well hydrated with plenty of fluids, exercising regularly, and getting enough sleep those with sickle cell disease may help their bodies remain strong and ward off fatigue and dehydration.

BOOKS

"Anemias Caused by Excessive Hemolysis: Sickle Cell Diseases." Section 11, Chapter 127 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.

Beutler, Ernest. The Sickle Cell Diseases and Related Disorders. Williams Hematology, edited by Ernest Beutler, et al. 5th ed. New York: McGraw-Hill, 1995.

Bloom, Miriam. Understanding Sickle Cell Disease. Jackson, MS: University Press of Mississippi, 1995.

The Editors of Time-Life Books. Sickle Cell Anemia. The Medical Advisor: The Complete Guide to Alternative & Conventional Treatments, Richmond, VA: Time-Life Inc., 1996.

Embury, Stephen H., et al., eds. Sickle Cell Disease: Basic Principles and Clinical Practice. New York: Raven Press, 1994.

"Pregnancy Complicated by Disease: Hemoglobinopathies." Section 18, Chapter 251 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.