Blood vessels throughout the body are vulnerable to vasoocclusive episodes associated with sickle cell anemia. This helps explain the wide-ranging effects of this disease, including involvement of the cardiovascular, ocular and other organ systems. Typically, a vasoocclusive event causes pain because the tissues beyond the blockage in the blood vessel do not receive an adequate supply of blood. Typically, pain lasting anywhere from a few hours to weeks can occur in the back, ribs and limbs. Pain may also develop in the chest, abdomen and joints. In severe cases, hospitalization may be required so the patient may receive pain medications and intravenous (I.V.) fluids.

Though some patients experience painful episodes once every few years, others may have several episodes a year. After repeated episodes, a patient may develop damage to the kidneys, lungs, bones, eyes and central nervous system. These crises can be precipitated by infections. Opioid pain medications may be used to treat moderate to severe pain.

Common forms of crisis include:

• Hemolytic crisis. This crisis results from the rapid destruction of damaged red blood cells.
  
  
• Splenic sequestration crisis. This is the result of red blood cells suddenly becoming trapped in the spleen, resulting in an enlarged spleen and low blood volume.  Urgent medical care is necessary.
  
  
• Aplastic crisis. This is the result of infection (caused by the parvovirus B19) causing the bone marrow to stop producing red blood cells.  It is characterized by a sudden decrease in hemoglobin counts, requiring urgent blood transfusion.

Sickle cell anemia can lead to a number of other complications, some of which are life-threatening. Possible complications include:

• Hand-foot syndrome. Occurs when blood vessels in the hands and feet are blocked, causing swelling, pain and fever. One or both hands or feet may be affected, with swelling typically beginning on the back of the hands or feet before migrating to the fingers or toes. Hand-foot syndrome may be the first symptom experienced by infants with sickle cell anemia.
  
  
• Pulmonary hypertension. Occurs when high blood pressure occurs in the blood vessels that supply the lungs. Pulmonary hypertension occurs in one-third of patients with sickle cell anemia, according to the National Institutes of Health (NIH). It can lead to heart failure, although treatments can help to control symptoms.

• Stroke. A potentially fatal event in which the flow of oxygen-rich blood to the brain is reduced. In a person with sickle cell anemia, a stroke may occur as the result of sickle cells obstructing blood flow to the brain. Common signs of stroke include weakness or numbness in the limbs, especially on one side of the body, sudden difficulty speaking or swallowing, or alteration of consciousness.  They occur more commonly in children younger than 10 years old.
  
  In 2005, scientists unveiled a genetic test they described as 98 percent accurate in predicting strokes in people who have sickle cell anemia. The test detects variations in genes called single nucleotide polymorphisms (SNPs).
  
  
• Acute chest syndrome. A life–threatening condition that causes chest pain, fever and breathing difficulty. It is the result of a lung infection or sickle cells becoming trapped in the lungs, and it can be indistinguishable from pneumonia. Recurrent episodes can cause lung damage.   
  
  
• Organ damage. As blood travels throughout the body, it delivers oxygen to the organs. When sickle cells block blood flow through the blood vessels they deprive the organs of necessary oxygen. This may result in damage to nerves and organs, including the kidneys, liver and spleen. In some cases, organ damage may be fatal. Necrosis (tissue death) of the hip and shoulder joints may occur, causing considerable disability, and may require joint replacement surgery (arthroplasty).
  
  
• Blindness. In people with sickle cell anemia, sickle cells can obstruct the tiny blood vessels of the eyes. This can damage the retina (the component of the eye which processes visual images) and may lead to blindness.
  
  
• Ulcers. People with sickle cell anemia may develop open sores on their legs. Known as ulcers, these sores are the result of sickle cells blocking blood flow that nourishes the skin. This results in death of the skin cells and causes sores to develop.
  
  
• Gallstones. Bilirubin is a substance produced from the breakdown of red blood cells. People with sickle cell anemia may have high levels of bilirubin in their blood, which can lead to gallstones.  This may be present in up to 50 percent of adults with this disease.
  
  
• Impotence. In men, sickle cell anemia can lead to priapism (painful erections). This is the result of sickle cells preventing the blood from flowing out of an erect penis. According to the NIH, about 10 to 40 percent of men with sickle cell anemia experience priapism. The condition can damage the penis and cause impotence.
  
  
• Infection. Sickle cells can cause damage to the spleen, an organ responsible for fighting infection. As a result, people with sickle cell anemia are at an increased risk of infection including pneumonia, meningitis (inflammation of the membranes covering the brain and spinal cord), influenza, hepatitis (inflammation of the liver), cholecystitis (inflammation of the gallbladder), osteomyelitis (bone infection) and urinary tract infection. Pneumonia infection is the leading cause of death in children with sickle cell anemia.
  
  
• Stunted growth in children. The lower levels of red blood cells associated with sickle cell anemia prevent the body from getting the oxygen and nutrients needed for children to grow to full potential. Inadequate levels of red blood cells also can delay puberty in some children.