Iron Disorder Anemia Sickle Cell Disease

Sickle cell anemia is a genetic disorder of the red blood cells caused by inheriting the gene hemoglobin S. Sickle cell anemia, or sickle cell disease, causes red blood cells to become rigid and sickle-shaped. Red blood cells affected by hemoglobin S cannot function properly, resulting in anemia symptoms, blood clots and painful episodes known as “sickle crisis.”

Who Gets Sickle Cell Anemia?

Anyone can inherit hemoglobin S from their parents. However, people of African descent are most at risk for sickle cell anemia. In the African American community, one out of every five hundred people is affected by sickle cell anemia. People of Spanish, Mediterranean, Middle Eastern and Indian ancestry also have a higher than normal risk of inheriting hemoglobin S.

Sickle cell anemia is an autosomal recessive disease, meaning a person must receive the hemoglobin S gene from both parents for sickle cell anemia symptoms to develop. A person with only one hemoglobin S gene is unlikely to develop sickle cell anemia symptoms. People possessing a single hemoglobin S gene are said to be sickle cell trait carriers.

If both parents have sickle cell trait, their children have a fifty percent chance of having normal red blood cells, a 25 percent chance of inheriting sickle cell trait and a 25 percent chance of developing sickle cell anemia. One in twelve African Americans is believed to be a sickle cell trait carrier.

Hemoglobin S Origins

Despite the many health complications caused by sickle cell anemia symptoms, hemoglobin S may have evolved as a survival trait. Some experts have concluded that hemoglobin S developed as a defense against malaria in North Africa. Hemoglobin S impairs the growth of the malaria parasite, so people with sickle cell trait are more likely to survive the disease than people with normal red blood cells.

Hemoglobin S and Red Blood Cells

Image of normal blood cell compared to a sickled cell.

Healthy red blood cells are round and flexible, allowing them to flow unhindered through blood vessels. Red blood cells affected by hemoglobin S assume a characteristic sickle or crescent moon shape. These abnormal red blood cells are rigid and can block small blood vessels, causing blood clots. A blood clot can damage organs and result in a painful sickle cell anemia symptom called a sickle crisis.

Hemoglobin S red blood cells are less stable than healthy blood cells. Normal red blood cells live an average of three to four months. The life expectancy of sickle cells is only ten to twenty days. As a result, hemoglobin S red blood cells die faster than they can be replaced, causing a chronic shortage of red blood cells that trigger anemia symptoms.

Sickle Cell Anemia Symptoms

Sickle cell anemia is present from birth, but anemia symptoms don’t usually develop until the fourth month of life, when the imbalance of red blood cells becomes significant enough to be noticeable. Some symptoms of sickle cell anemia resemble iron deficiency anemia symptoms, including fatigue and shortness of breath.

Other sickle cell anemia symptoms include:

  • abdominal pain
  • bone pain
  • delayed onset of puberty
  • fever
  • growth delays
  • high risk of infection
  • jaundice
  • joint pain
  • leg ulcers
  • rapid heartbeat
  • sickle crisis.

Less common sickle cell anemia symptoms include:

  • blood in urine
  • chest pain
  • excessive thirst
  • excessive urination
  • priapism (an unwanted and painful erection)
  • vision problems.

Sickle Crisis

A sickle crisis is a painful episode that periodically affects people with sickle cell anemia. A sickle crisis occurs when sickle-shaped red blood cells block blood vessels. The resulting blood clot cuts off blood supply to internal organs, causing organ damage. Varieties of sickle crisis include:

  • acute chest syndrome: This is a sickle crisis caused by trapped hemoglobin S red blood cells in the lungs. The resulting life-threatening lung congestion resembles pneumonia, causing chest pain, difficulty breathing and fever. Emergency medical attention is required to reopen the respiratory airways.
  • aplastic sickle crisis: Systemic infections, most often viral, halt production of red blood cells in the bone marrow.
  • hand/foot syndrome: This sickle crisis is often the first sickle cell anemia symptom to develop in infants. Red blood cells block blood vessels in the hands and feet, causing pain and fever.
  • hemolytic sickle crisis: Caused by a sudden breakdown of red blood cells, this condition can be life-threatening.
  • splenic sequestration sickle crisis: This crisis is caused by an enlarged spleen that traps red blood cells.

Some people with sickle cell anemia may experience one sickle crisis every few years. Other people experience multiple sickle crisis episodes over the course of a single year. A sickle crisis can last a few hours to several days.

Sickle crisis symptoms vary depending on the blood clot’s location, but they often include back pain, pain in the long bones of the body and chest pain. A severe sickle crisis can result in hospitalization and requires narcotics for pain relief.

Diagnosing Sickle Cell Anemia

A physical examination of the patient may reveal signs of paleness, growth retardation and jaundice — yellow eyes and skin. In African Americans jaundice is usually detected by yellowness of the eyes. A history of possible anemia symptoms and evidence of sickle crisis episodes is recorded.

Blood tests are required for a definitive sickle cell anemia diagnosis. A special blood test called hemoglobin electrophoresis is used to detect hemoglobin S, which can confirm the diagnosis.

Sickle Cell Anemia Complications

Untreated sickle cell anemia and repeated sickle crisis episodes can result in serious health complications. Infections and organ failure due to sickle crisis damage once reduced the life expectancy of a person with sickle cell anemia to twenty or thirty years. Advances in sickle cell treatment and management of anemia symptoms have increased the average lifespan to between forty and fifty years.

Sickle cell anemia complications include:

  • blindness
  • cholecystitis (gallbladder inflammation)
  • erectile dysfunction
  • gallstones
  • joint destruction
  • kidney necrosis (tissue death)
  • osteomyelitis (bone inflammation)
  • pneumonia
  • spleen dysfunction
  • strokes
  • urinary tract infections.

Sickle Cell Anemia and Narcotic Abuse

There is a persistent myth that people with sickle cell anemia are particularly susceptible to narcotic abuse. This is false: sickle cell anemia patients are no more likely to abuse narcotics than any other chronic pain group.

Treatment of Sickle Cell Anemia

Sickle cell anemia treatment focuses on reducing sickle crisis incidents and managing anemia symptoms. Folic acid supplements are recommended to counter the rapid death of hemoglobin S red blood cells. Regular eye examinations are required to evaluate the risk of retinal damage caused by blood clots.

Treatments for sickle cell anemia complications include:

  • antibiotics for infections
  • emergency surgery for strokes
  • gallbladder removal
  • hip replacement for joint destruction
  • irrigation or surgery to relieve priapism (painful erections)
  • kidney dialysis
  • kidney transplant
  • optical surgery
  • wound care for leg ulcers.

Bone Marrow Transplants

Bone marrow transplants and gene therapy offer a theoretical cure for sickle cell anemia by replacing the hemoglobin S gene with healthy hemoglobin. Unfortunately, the high risks associated with bone marrow transfers, combined with the scarcity of suitable donors, means bone marrow transplants are an option for only a small number of sickle cell anemia cases. Research testing the safety and efficacy of gene therapy is under way.

Sickle Crisis Treatment

Treatment for a sickle crisis focuses on pain management. Analgesics (pain relievers) and fluid intake are the primary treatments, and can usually be performed on an outpatient basis. Severe sickle crisis pain may require hospitalization for narcotics and intravenous fluids.

Hydroxyurea and Sickle Crisis

Hydroxyurea (or hydrea) has been used in sickle cell anemia treatment to reduce the frequency of sickle crisis episodes, especially with a specific type of sickle crisis called acute chest syndrome. Hydroxyurea also appears to reduce the need for blood transfusions.

Some physicians are concerned that hydroxyurea may cause leukemia over the course of long-term treatment of sickle cell anemia. As yet, no definitive study has satisfactorily proven or disproven this claim.


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Miller, J. A., McMillan, S. K, et al. (reviewed 1993, March). Sickle cell trait. Department of Pediatrics, Children’s Hospital of Iowa.

National Library of Medicine. (updated 2004 June 1). Hemoglobin electrophoresis. MedlinePlus Medical Encyclopedia.

National Library of Medicine. (updated 2003, October 28). Sickle cell anemia. MedlinePlus Medical Encyclopedia.

National Library of Medicine. (updated 2005, February 1). Sickle cell test. MedlinePlus Medical Encyclopedia.