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    Preserving spleen and brain function in sickle cell patients

    Jane S. Hankins, MD, MS

    Increasing the level of normal hemoglobin in children with sickle cell anemia might prevent the long term damage to their spleens and brains that commonly occurs with this disease, according to St. Jude researchers.

    The investigators found that some children with sickle cell anemia who already suffered damage to their spleens completely recovered after being treated with hydroxyurea, while others avoided the problem entirely; and in many children with brain lesions (small areas of injury), the damage did not worsen, according to Jane Hankins, MD, Hematology. Hankins is first author of a report on this work that appears in the online prepublication version of Pediatric Blood and Cancer.

    Sickle cell anemia is a genetic disease in which red blood cells carry an abnormal form of hemoglobin—the oxygen-carrying protein in blood. This abnormal hemoglobin causes red cells to twist, or sickle, which in turn breaks apart the cells or makes them stiff and unable to squeeze through tiny blood vessels deep inside body tissues and internal organs. These cells clog and twist blood vessels, starving tissues of oxygen. This causes pain as well as continual damage over the years to the spleen, brain, kidneys and lungs.

    Damage to the spleen and brain is especially dangerous for children with sickle cell anemia because it causes serious medical complications that worsen as the children get older.

    “The spleen plays an important role in the immune system’s defense of the body, so children with spleen damage are at increased risk of life threatening infections from certain bacteria,” Hankins said. “And reduction of oxygen to the brain can cause stroke.”

    The investigators did a retrospective study of the medical records of 43 children with sickle cell anemia treated with hydroxyurea at St. Jude for times ranging from 0.2 to 8.6 years and who had undergone a special test that determines how well their spleen worked before and during treatment. In addition, the team studied the results of brain imaging tests for 25 children who had undergone these procedures before and during treatment. The children each received the maximum dose of hydroxyurea they could tolerate in order to increase the likelihood that they would receive the most benefit from the drug.

    The St. Jude team found that spleen function was either preserved or restored in about 20 percent of the patients. Complete recovery of spleen function occurred in six children, and two patients with normal spleen function before treatment maintained normal function while receiving hydroxyurea. These eight children also had a greater amount of normal hemoglobin while on hydroxyurea therapy than did patients whose spleens had stopped working. “This shows that children with higher hemoglobin concentrations during therapy are likely to have good spleen function,” Hankins said.

    Among the 25 children who had undergone brain imaging procedures, seven (28 percent) had areas of silent brain ischemia—areas that had suffered lack of oxygen with disrupted brain function—before starting hydroxyurea treatment. Another 17 children (68 percent) had twisted blood vessels in some areas of the brain before receiving the drug. During treatment with hydroxyurea, only one of these children developed another area of damage (slight bleeding) and none of the 25 children developed signs of brain ischemia or stroke during follow-up studies that lasted up to three years.

    “Although hydroxyurea can trigger the body to make fetal hemoglobin that helps prevent red cells from sickling, we didn’t know whether the drug could also preserve the function of the spleen and prevent worsening of brain lesions,” said the report’s senior author, Russell Ware, MD, PhD, Hematology chair. “The results of our study suggest that at least some children with sickle cell disease will be able to prevent organ damage by using hydroxyurea.”

    Results of the study also strongly suggest that children should carefully adhere to their treatment and that doctors should increase the dose of hydroxyurea to the maximum amount tolerated by each child in order to maintain high levels of normal hemoglobin, Hankins said. “Our findings add to the growing evidence that hydroxyurea therapy protects children who have sickle cell disease from the long-term problems of organ damage,” Ware said.

    Other authors of the paper include Kathleen Helton, MD, and Beth McCarville, MD, both of Radiological Sciences; Chin-Shang Li, PhD, Biostatistics; and Winfred Wang, MD, Hematology.

    July 2007