Tag: sickle cell disease

Sickle Cell Anemia

Sickle cell disease is a blood cell disorder that affects a lot of Americans, especially those of African descent. The disease is a result of a genetic defect that changes the structure of hemoglobin. This alteration in hemoglobin causes normally round red cells to become sickle in shape as well as sticky and deformed. As a result, these deformed red cells block perfusion of red blood cells into circulation and vital organs and affects the vasculature resulting in severe pain, organ damage and sometimes stroke.

Management of sickle cell disease includes blood transfusion, hydorxyurea and pain management. The long-term administration of hydroxyurea to stimulate the production of fetal hemoglobin is a form of therapy that provides relief in that fetal hemoglobin essentially protects the red cells from sickling. The transfusion of red cells lowers the amount of sickle hemoglobin levels.

Transplantation of hematopoietic stem cells from HLA-identical siblings can be curative in several nonmalignant hematologic disorders, including aplastic anemia, β-thalassemia major, congenital immunodeficiency disorders, and certain inborn errors of metabolism. Pilot studies of bone marrow transplantation for the treatment of young patients with symptomatic sickle cell disease have demonstrated eradication of the underlying disease with low transplantation-related mortality (Bhatia and Walters, 2007).

The process for successful bone marrow transplant to cure sickle cell involves administration of chemotherapy or immunosuppressive drugs to eradicate all the cells.  Now, doctors have developed a more successful regimen where patients take immunosuppressive drugs with a low dose body irradiation, a treatment much less harsh than chemotherapy. Next, donor cells from a healthy and tissue-matched sibling are transfused into the patient. Stem cells from the donor produce healthy new blood cells in the patient, eventually in sufficient quantity to eliminate symptoms. In many cases, sickle cells can no longer be detected. Patients must continue to take immunosuppressant drugs for at least a year.

In the reported trial, published online in the journal Biology of Blood & Marrow Transplantation, physicians from the University in Illinois Chicago transplanted 13 patients, 17 to 40 years of age, with a stem cell preparation from the blood of a tissue-matched sibling. In a further advance of the NIH procedure, the physicians successfully transplanted two patients with cells from siblings who matched but had a different blood type (Parmet, 2015)

Stem cell transplantation has proven itself to provide cures for a lot of hematologic malignancies, now it is successfully finding its way to cure other hematologic abnormalities, including sickle cell anemia.  This continued advancement in medicine will provide relief to a lot of patients who are suffering from sickle cell disease.

References

  1. Bhatia, M., & Walters, M. C. (2007). Hematopoietic cell transplantation for thalassemia and sickle cell disease: past, present and future. Bone Marrow Transplantation, 41(2), 109-117. doi:10.1038/sj.bmt.1705943
  1. Parmet, S. (2015). Adults with sickle cell disease cured with stem cell transplants. Retrieved March 25,2017, from https://news.uic.edu/cure-for-sickle-cell

 

ledesma_small

-Carlo Ledesma, MS, SH(ASCP)CM MT(ASCPi) MT(AMT) is the program director for the Medical Laboratory Technology and Phlebotomy at Rose State College in Midwest City, Oklahoma as well as a technical consultant for Royal Laboratory Services. Carlo has worked in several areas of the laboratory including microbiology and hematology before becoming a laboratory manager and program director.

A Strategy for Patients with Sickle Cell Disease

Transfusion of red blood cells (RBCs) is a cornerstone of treatment to prevent the complications of sickle cell disease (SCD). SCD is caused by a mutation of the β-globin gene, resulting in glutamic acid being substituted by valine at position 6. The mutation results in an abnormal hemoglobin (Hb SS) that aggregates into a rigid sickle-shape under certain conditions. Individuals with SCD frequently require transfusion of RBCs to treat acute pain crisis (i.e. acute chest syndrome) and prevent chronic complications (i.e. stroke). RBC transfusion helps SCD patients by providing RBCs with hemoglobin A thus decreasing the amount of HbSS RBCs that can sickle and contribute to pain crisis and chronic complications. Unfortunately, alloimmunization to non-ABO RBC antigens is a potential complication of any patient receiving chronic transfusion therapy. The most life-threatening consequence of alloimmunization in SCD is the development of a delayed hemolytic transfusion reaction with hyperhemolysis. Alloimmunization also puts SCD patients at increased risk of receiving an incompatible transfusion due to difficulty in finding compatible blood and increases costs for the health care system.

Antigen matching beyond standard ABO and Rh typing can help reduce the alloimmunization rate in chronically transfused patients. A widely accepted antigen matching strategy used by transfusion services is to initially provide Rh and Kell-matched RBC units to SCD patients, even if the patient has not yet made an alloantibody (i.e. antibody screen negative) since the Rh (D, C, c, E and e) and Kell (K) antigens are among the most immunogenic.  Providing Rh and K-matched RBC units continues until the patient proves to be an antibody former (i.e. anti-Jk(b)), after which the transfusion service provides fully phenotype matched RBCs for non-emergent transfusion when available.  A “full” phenotype usually includes Rh, K, Jk(a), Jk(b), Fy(a), Fy(b), M, N, S and s.

In summary, the strategy for patients with SCD is as follows:

  1. Determine the patient’s full RBC phenotype (D, C, c, E, e, K, Kidd, Duffy, M, N, S, s) before transfusions begin. If transfusions already started, consider molecular testing.
  2. Provide Rh (D, C, c, E, e) and K-matched RBCs until the patient proves to be an antibody former.
  3. If the patient proves to be an antibody former, provide full phenotype matched RBC units to attempt to prevent any additional antibody formation and it becomes increasingly impossible to find compatible units.

 

Rogers

-Thomas S. Rogers, DO is a second-year resident at the University of Vermont Medical Center, a clinical instructor at the University of Vermont College of Medicine, and the assistant medical director of the Blood Bank and Transfusion Medicine service.