Sickle cell anemia is an inherited blood disorder that causes lifelong disease. Beside anemia or low blood count, individuals afflicted with this disorder also have recurrent painful episodes and malfunction of some organs.
Recognized in Africa as a disease before a physician described it in 1910, the red blood cells of patients with sickle cell anemia appeared to have a sickle-shape. In 1940, the association between abnormal hemoglobin and the tendency of red blood cells to sickle was made. In 1949 Pauling and associates noted that sickle hemoglobin (HbS) had an abnormal electrophoretic pattern, and in 1957 Ingram reported the substitution of valine for glutamic acid as the sixth amino acid of beta-globin. These studies concluded that the hemoglobin in the red blood cells of patients with sickle cell anemia was different on a molecular basis from those individuals who were not afflicted with the disease.
The red blood cells of patients with sickle cell disease can change from the normal disk like shape to an “S” shape or sickle shape under certain conditions. These conditions include a decrease in available oxygen such as being a passenger on an airplane, during a viral infection especially when the lungs are involved, during fever or when a state of dehydration occurs. Sickle shaped red blood cells cannot carry oxygen and increase the thickness of the blood. As a result, certain parts of the body may not receive enough oxygen and blood clots may occur in smaller blood vessels due to the increased viscosity or thickness of the blood.
While some of the red blood cells assume the sickle shape only under certain conditions, some cells are irreversibly sickled. These cells do not survive as long in the circulation and account for some of the persisting anemia in these patients.
Who is likely to develop sickle cell anemia?
Every individual receives one gene from each parent that determines the type of hemoglobin in his or her red blood cells. Most individuals in the United States receive an “A” gene from each parent so the hemoglobin is termed HbAA. Patients with sickle cell anemia receive an “S” gene from each parent and this gives rise to the abnormal hemoglobin (HbSS) where valine is substituted for glutamic acid. Carriers for sickle cell anemia, who are termed sickle trait, typically receive an “A” gene from one parent and an “S” gene from the other parent and have HbAS.
The prevalence of sickle trait among African American babies in the United States is eight to ten percent and up to thirty percent in Africa. There are approximate fifty thousand to sixty thousand patients with sickle cell anemia in the United States and four thousand to five thousand unborn children are at risk for the disease each year. Babies can be afflicted with the disease if both parents are carriers, both parents have the disease or if one parent is a carrier and one parent has the disease. If one parent has neither the disease nor the carrier state, then the baby cannot have the full-blown disease although a baby could be affected with the carrier state.
What are the symptoms of sickle cell disease?
Many teens have no symptoms between sickle crises and adapt to the anemic state. However, when the sickle cells develop, blood clots may occur and the most common symptom is pain. These so called painful crises are precipitated by cold, dehydration, infection, stress, menstruation or alcohol intake. Adolescents may have fever, swelling, tenderness, nausea and vomiting associated with these painful crises.
The anemia of sickle cell disease may worsen under certain conditions. In these cases, the teen may have increased destruction of red blood cells and there also may be an associated temporary shutdown in the synthesis of new red blood cells. Yellow eyes, increasing fatigue and shortness of breath could be symptoms associated with the worsening anemia.
Although children with sickle cell disease usually have slower growth and development, by the teenage years most patients have caught up in height. However, adolescents tend to be thin compared to their height. The onset of puberty may also be delayed. Patients may have problems concentrating their urine, and in women, their fertility is reduced. Gallstones are more common in individuals with sickle cell disease. Males with sickle cell disease are prone to priapism, which is a painful persistent penile erection. When sickling occurs in the blood vessels of the penis, the teen may develop priapism. This could lead to impotence in older adolescents.
Teens with hemoglobin HbAS or sickle trait are healthy and have a normal lifespan without symptoms related to the trait. They are allowed full participation in sports, but should be counseled that they could bear or father a child with full-blown sickle cell disease if their partner has the trait or the disease.
How is sickle cell disease evaluated?
Prenatal diagnosis can be done through testing of the amniotic fluid in the second trimester. Some states offer screening of newborns for sickle hemoglobin, and by three months of age babies with sickle cell disease may have sickle shaped red blood cells on a blood smear. A hemoglobin electrophoresis should be performed in patients suspected of having sickle cell disease.
How is sickle cell disease treated?
Adolescents with sickle cell disease should have a primary care clinician as well as a specialist skilled and knowledgeable in the treatment of this disorder. Routine healthcare is necessary to be certain that immunizations are current; the patient receives an annual influenza vaccination, has a pneumococcal and hemophilus vaccination and is counseled on the benefits of other vaccines including meningococcal and varicella vaccines. Many patients are also started on daily antibiotics to prevent infection and multiple vitamins to help the body make new red blood cells. Sexually active teens should be counseled on effective methods of birth control.
Adolescents with sickle cell disease should have a strong relationship with a primary care clinician who has interest and expertise in adolescent issues. These teens may have issues in regard to growth and development, fertility, sports participation and emotional problems all associated with the chronic disease state caused by sickle cell disease. For example, adolescents with sickle cell disease do have a degree of cognitive impairment that could be subtle to more global in nature. Academic performance is likely to be compromised, and adolescents with this disease have a higher incidence of school dropout or poor school achievement. This will impact on the teen’s future employment and financial status. Counseling is indicated for these issues.
The primary care clinician should provide ready accessibility if the teen with sickle cell disease develops an illness. Teens with this illness are more likely to develop serious bacteria infections that could require aggressive antibiotic therapy or inpatient hospital treatments.
A hematologist should follow teens with sickle cell disease. There are ongoing studies to evaluate modalities to lessen pain or prevent crises. Hydroxyurea is now being used to prevent sickle cell crises. Bone marrow transplantation has been used successfully for sickle cell anemia. Gene therapy technology may provide some promise for the future of patients with sickle cell disease.
How is sickle cell disease prevented?
Couples who carry the sickle cell trait gene should be counseled. A child whose parents both have sickle trait has a twenty-five percent chance of receiving both sickle genes and therefore develop sickle cell anemia. The child has a fifty percent chance of receiving one sickle gene and then have sickle trait. And there is a twenty-five percent chance the child could receive no sickle genes.
Related topics:
Anemia, body image, chronic illness, genetic disease, growth and development, immunizations, sports
