9 of 10 Sickle Cell Patients Sustain Reversal of Disease with Stem Cell Transplant
By Barbara Lock, MDDecember 10, 2009
The finding that 9 of 10 patients with sickle cell disase reversed their disease with nonmyeloablative stem cell transplant, published today in the New England Journal of Medicine, could literally be the beginning of the end for this horrible and debilitating disease.
The key feature of the procedure, that it is nonmyeloablative, means that, unlike as occurs in the case of some other types of bone marrow or stem cell transplants, the host patient's native blood-producing tissue is not entirely wiped out. The host patients appear to develop a sort of chimera, or mixture, of blood-producing tissue; partially their own, and partially that of the donor.
The authors also report that the average hemoglobin level in the body of the subjects increased from 9 grams per deciliter (too low) to 12.6 grams per deciliter (normal).
Sickle cell anemia is a disease which occurs in patients of African, Middle Eastern, or Indian descent; the genes that confer the disease code for an abnormal type of hemoglobin, which is the molecule in red blood cells that carry oxygen through the body. Parents of children with sickle cell anemia are sometimes unaware of the risk of transferring the disease to their children, because persons with only one copy of the gene may have no symptoms. In fact, persons with one copy of the sickle cell gene have a survival advantage when exposed to malaria; this is why the gene for sickle cell anemia has persisted in human populations.
When a person gets two copies of the abnormal gene, one from the mother and one from the father, the abnormal hemoglobin becomes the predominant type of hemoglobin produced by the body. The abnormal hemoglobin will tend to line up in a cell, forming a sort of rod or polymer of hemoglobins, under conditions of low oxygen, cold, or dehydration. This causes the red blood cell, which looks kind of like a doughnut without the hole, to stretch out into a pointy half-moon shape, or sickle. The sickled cells then "catch" in the small blood vessels, and prevent flow of normal blood cells, thus preventing delivery of oxygen to tissues. These episodes, called crises, can be extremely painful, and occasionally life-threatening, as can occur when the cells sickle in the blood supply to the lungs or to the brain. When sickling in the lungs occurs (chest crisis), patients may become critically ill, requiring an exchange of blood (exchange transfusion). When sickling in the brain occurs, patients may have a stroke.
While many patients with sickle cell disease can manage their illness carefully at home with attention to hydration and pain control, others have severe disease or develop regrettable habits, and may require very high doses of narcotic pain medication such as dilaudid, morphine, or demerol. Most emergency department staff know the sickle cell patients very well, for they may present for treatment ten or more times per month.
One of the important side effects of the stem cell transplant that reversed sickle cell disease in these patients was that of opiate withdrawal. Opiate narcotics are derived from the poppy plant, related to opium and morphine. This class of medication is the primary and most important type of pain medication available to relieve human suffering today, and patients who require opiate pain medication to relieve suffering should not be arbitrarily denied treatment simply because of the known risk of tolerance. Non-steroidal anti-inflammatory medications have not been shown to work as well or better than opiates for sickle cell crisis. (Bartolucci, Hardwick, Wright) Opiate withdrawal, unlike alcohol withdrawal or benzodiazepine withdrawal, is not considered life-threatening, just very unpleasant.
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