Health Encyclopedia

Sickle cell anemia

Definition

Sickle cell anemia is a disease passed down through families in which red blood cells are an abnormal crescent shape. (Red blood cells are normally shaped like a disc.)

Alternative Names

Anemia - sickle cell; Hemoglobin SS disease (Hb SS); Sickle cell disease

Causes, incidence, and risk factors

Sickle cell anemia is caused by an abnormal type of hemoglobin called hemoglobin S. Hemoglobin is a protein inside red blood cells that carries oxygen. Hemoglobin S, however, distorts the red blood cells' shape. The fragile, sickle-shaped cells deliver less oxygen to the body's tissues, and can break into pieces that disrupt blood flow.

Sickle cell anemia is inherited as an autosomal recessive trait. This means it occurs in someone who has inherited the hemoglobin S gene from both parents. Sickle cell disease is much more common in people of African and Mediterranean descent. It is also seen in people from South and Central America, the Carribbean, and the Middle East.

Someone who inherits hemoglobin S from one parent and normal hemoglobin (A) from the other parent will have sickle cell trait. Someone who inherits hemoglobin S from one parent and another type of abnormal hemoglobin from the other parent will have another form of sickle cell disease, such as thalassemia.

Although sickle cell disease is present at birth, symptoms usually don't occur until after 4 months of age. Sickle cell anemia may become life threatening. Blocked blood vessels and damaged organs can cause acute painful episodes, or "crises." There are several types of crises:

Hemolytic crisis occurs when damaged red blood cells break down
Splenic sequestration crisis is when the spleen enlarges and traps the blood cells
Aplastic crisis results when an infection causes the bone marrow to stop producing red blood cells

These painful crises, which occur in almost all patients at some point in their lives, can last hours to days, affecting the bones of the back, the long bones, and the chest. Some patients have one episode every few years, while others have many episodes per year. The crises can be severe enough to require admission to the hospital for pain control and intravenous fluids.

Repeated crises can cause damage to the kidneys, lungs, bones, eyes, and central nervous system.

Symptoms

Common symptoms include:

Attacks of abdominal pain
Bone pain
Breathlessness
Delayed growth and puberty
Fatigue
Fever
Jaundice
Paleness
Rapid heart rate
Susceptibility to infections
Ulcers on the lower legs (in adolescents and adults)

The patient may also have:

Bloody urine (hematuria)
Chest pain
Excessive thirst
Frequent urination
Painful erection (priapism; this occurs in 10 - 40% of men with the disease)
Poor eyesight/blindness
Strokes
Skin ulcers

Signs and tests

Tests commonly performed to diagnose and monitor patients with sickle cell anemia include:

Patients with sickle cell may have abnormal results on certain tests, as follows:

Amount of oxygen in the blood may be decreased
CT scan or MRI may show strokes in certain circumstances
Elevated bilirubin
High serum creatinine
High serum potassium
High white blood cell count
Peripheral smear displays sickle cells
Serum hemoglobin will be decreased
Urinary casts or blood in the urine

Treatment

Patients with sickle cell disease need continuous treatment, even when they are not having a painful crisis. Supplementation with folic acid, an essential element in producing red blood cells, is required because of the rapid red blood cell turnover.

The purpose of treatment is to manage and control symptoms, and to try to limit the frequency of crises.

During a sickle crisis, certain treatments may be necessary. Painful episodes are treated with analgesics and enough liquid intake. Treatment of pain is critical. Non-narcotic medications may be effective, but some patients will require narcotics.

Hydroxyurea (Hydrea) is a drug used fro some patients to reduce the number of episodes of pain (including chest pain and difficulty breathing). It does not work for everyone.

Antibiotics and vaccines are given to prevent bacteria infections, which are common in children with sickle cell disease.

Additional treatments for complications may include:

Dialysis or kidney transplant for kidney disease
Drug rehabilitation and counseling for the psychological complications
Gallbladder removal (if there is significant gallstone disease)
Hip replacement for avascular necrosis of the hip (death of the joint)
Irrigation or surgery for priapism (persistent, painful erections)
Partial exchange transfusion for acute chest syndrome
Surgery for eye problems
Transfusions or surgery for brain problems, such as strokes
Wound care, zinc oxide, or surgery for leg ulcers

Bone marrow transplants can cure sickle cell anemia. However, very few people with this disease are able to find a suitable donor. Bone marrow transplantation may also include risks, including infection and rejection.

Support Groups

Sickle cell anemia, like other chronic, life-threatening diseases, can cause great stress to the patient and family members. Joining a support group, where members share common experiences and problems, can relieve this stress.

See sickle cell anemia - support group.

Expectations (prognosis)

In the past, death from organ failure often occurred between the ages of 20 and 40 in most sickle-cell patients. More recently, because of better understanding and management of the disease, patients live into their forties and fifties.

Causes of death include organ failure and infection. Some people with the disease experience minor, brief, and infrequent episodes. Others experience severe, prolonged, and frequent episodes resulting in many complications.

Complications

Acute chest syndrome
Blindness/visual impairment
Death
Erectile dysfunction (as a result of priapism)
Gallstones
Infection, including pneumonia, cholecystitis (gallbladder), osteomyelitis (bone), and urinary tract infection
Joint destruction
Leg ulcers
Loss of function of the spleen
Multisystem disease (kidney, liver, lung)
Narcotic abuse
Neurologic (brain and nervous system) symptoms and stroke
Parvovirus B19 infection resulting in aplastic crisis
Recurrent aplastic and hemolytic crises resulting in anemia and gallstones
Splenic sequestration syndrome
Tissue death of the kidney

Calling your health care provider

Call your health care provider if acute painful crises occur or at the first sign of any infection.

Prevention

Sickle cell anemia can result only when two carriers with sickle cell trait have a child together. Therefore, genetic counseling is recommended for all carriers of sickle cell trait. About 1 in 12 African-Americans has sickle cell trait. Diagnosis of sickle cell anemia during pregnancy is also available.

Prompt treatment of infections, adequate oxygenation, and preventing dehydration may prevent sickling of red blood cells. Antibiotics and vaccinations may prevent infections.

The patient should have regular physical exams every 3 - 6 months to ensure the patient is getting adequate nutrition, maintains proper activity levels, and receives proper vaccinations. Regular eye exams are also recommended.

PREVENTING INFECTIONS

People with sickle cell anemia need to keep their immunizations up to date, including influenza, pneumococcal, meningococcal, hepatitis B, and influenza.
Some patients may receive antibiotics to prevent infections.

PREVENTING CRISES

Parents whose children have sickle cell disease should encourage their children to lead normal lives. However, in order to decrease the occurrence of sickle cell crises, consider the following precautions:

To prevent loss of oxygen from tissues, avoid the following:

Demanding physical activity, especially if the spleen is enlarged
Emotional stress
Environments with low oxygen content (high altitudes, non-pressurized airplane flights)
Smoking
Known sources of infection

To promote proper hydration:

Recognize signs of dehydration
Avoid too much exposure to the sun
Provide access to fluids, both at home and away

To avoid sources of infection:

Keep child properly immunized as recommended by the health care provider
Consider having the child wear a Medic Alert Bracelet
Share above information with teachers and other caretakers as appropriate

Be aware of the effects that chronic, life-threatening illnesses can have on siblings, marital relationships, parents, and the child.

References

Lee MT, Piomelli S, Granger S, et al. Stroke Prevention Trial in Sickle Cell Anemia (STOP): extended follow-up and final results. Blood. Aug 1, 2006;108(3):847-52.

Mehta SR, Afenyi-Annan A, Byrns PJ, Lottenberg R. Opportunities to improve outcomes in sickle cell disease. Am Fam Physician. 2006 Jul;15;74(2):303-10.

Saunthararajah Y, Vichinsky EP, Embury SH. Sickle cell disease. In: Hoffman R, Benz Jr. EJ, Shattil SJ, Furie B, Cohen HJ, eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston;2005;chap 37.

U.S. Preventive Services Task Force. Screening for Sickle Cell Disease in Newborns: U.S. Preventive Services Task Force Recommendation Statement. Agency for Healthcare Research and Quality, Rockville, MD. Sep 2007:AHRQ Publication No. 07-05104-EF-2.

Review Date:6/10/2008
Reviewed By:James R. Mason, MD, Oncologist, Director, Blood and Marrow Transplantation Program and Stem Cell Processing Lab, Scripps Clinic, Torrey Pines, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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