Sickle Cell Disease

Sickle cell disease encompasses a group of disorders characterized by intermittent episodes of hemolysis (destruction of red blood cells) resulting in chronic anemia, pain crises, and chronic and acute organ dysfunction. Other complications include an improperly functioning spleen, increased susceptibility to infections and other multi-system manifestations. Symptoms begin in infancy or childhood and require life-long management and care to minimize morbidity and maintain a good quality of life. The disorders are associated with mutations in the HBB gene.

Sickle cell disease is inherited in an autosomal recessive manner. An individual who is affected has two gene changes (mutations) in the HBB gene. Parents of an affected individual usually each have one gene mutation and one normal working copy of the HBB gene. Thus, in every pregnancy of a couple in which both members have been identified as being a carrier for sickle cell disease, also called having sickle cell trait, there is a 1 in 4 (25%) chance of having a child affected with the disease. If one parent has sickle cell disease and the other parent is identified as being a carrier, the risk to have a child affected with the disease increases to 1 in 2 (50%).

For families at risk of having a child with sickle cell disease, prenatal diagnosis is available during pregnancy. However, some couples would rather not initiate an affected pregnancy and instead opt for PGD for sickle cell disease.

In a PGD cycle, embryos created by IVF are cultured in the laboratory for 3 days at which time they contain approximately 8 cells (Embryos at this point are called blastomeres). Embryos with normal development on Day 3 are biopsied using micromanipulation techniques. This involves the use of very fine glass needles and tools under microscopic observation and control to remove 1or 2 cells from each blastomere for analysis.

At this early stage of embryological development, the blastomeres are totipotent; they are still capable of forming cells of any organ or tissue. Removal of a few of the cells of the early embryo does not alter the ability of that embryo to develop into a complete, normal pregnancy and child. Data from many years of PGD in animals and approximately 1200 live births in humans indicate that PGD does not lead to an increase in birth defects or chromosomal disorders.

When a PGD biopsy is done, 1-2 cells are removed from the embryo. In order to obtain results of the biopsy, the cell removed must contain a nucleus, as the nucleus contains the genetic information necessary for testing. Analysis of the HBB gene for sickle cell anemia is detected on cells prior to implantation to determine which embryos are selected for transfer into a woman’s uterus. Thus, the chance to have a healthy unaffected pregnancy is greatly increased.

For more information about Genetics & IVF Institute's PGD for aneuploidy,
please call (800) 654-4363 or (703) 698-7355
and ask to speak with the PGD counselor OR email PGD@givf.com.