Sickle cell anemia
There is still no cure for sickle cell disease other than experimental transplantation procedures, but treatments for complications of sickle cell have prolonged the lives of many patients who are now living into adulthood.
The hallmark of sickle cell disease is the sickle cell crisis (also sometimes known as a vaso-occlusive crisis), which is an episode of pain. It is the most common reason for hospitalization in sickle cell disease. The pattern may occur as follows:
Episodes cannot be predicted, and they vary widely among different individuals. Episodes sometimes become less frequent with increasing age. Generally, people can resume a relatively normal life between crises. Most patients are pain-free between episodes although pain can be chronic in some cases.
Acute chest syndrome (ACS) occurs when the lung tissues are deprived of oxygen during a crisis. It can be very painful, dangerous, and even life threatening. It is a leading cause of illness among sickle cell patients and is the most common condition at the time of death. At least one whole segment of a lung is involved, and the following symptoms may be present:
Pain often lasts for several days. In about half of patients, severe pain develops about 2 - 3 days before there are any signs of lung or chest abnormalities. Acute chest syndrome is often accompanied by infections in the lungs, which can be caused by viruses, bacteria, or fungi. Pneumonia is often present. A dull, aching pain usually follows, which most often ends after several weeks, although it may persist between crises.
Causes of Acute Chest Syndrome. Primary causes of acute chest syndrome include:
In about half of cases, the cause cannot be established. Some cases of acute chest syndrome may result from treatments of the crisis, including from administration of opioids (which reduce oxygen) or excessive use of intravenous fluids. Other lung diseases may also trigger ACS.
Severity of Acute Chest Syndrome. The mortality rates for ACS are around 2% in children and 4% in adults. The syndrome and its long-term complications are the major causes of death in older patients. The longer a patient survives, the greater is the damage done by repetitive sickle cell crises in the chest and lungs.
The following destructive effects can occur:
Infections are common and an important cause of severe complications in sickle cell patients. Before early screening for sickle cell disease and the use of preventive antibiotics in children, 35% of infants with sickle cell died from infections. Fortunately, with screening tests for sickle cell now required for newborns, and with the use of preventive antibiotics and immunizations in babies who are born with the disease, this terrible mortality rate has dropped significantly.
Infections in Infants and Toddlers with Sickle Cell Disease. The most common organisms causing infection in children with sickle cell disease include:
Such infections pose a grave threat to infants and very young children with sickle cell disease. They can progress to fatal pneumonia with devastating speed in infants, and death can occur only a few hours after onset of fever. The risk for pneumococcal meningitis, a dangerous infection of the central nervous system, is also significant.
Infections in Children and Adults. Infections are also common in older children and adults with sickle cell disease, particularly respiratory infections such as pneumonia, kidney infections, and osteomyelitis, a serious infection in the bone. (The organisms causing them, however, tend to differ from those in young children.) Infection-causing organisms include:
About 30% of patients with sickle cell disease have pulmonary hypertension. Pulmonary hypertension is a serious and potentially deadly condition that develops when pressure in the arteries of the lungs increases. It is an often unrecognized complication and cause of death in sickle cell disease. Many doctors recommend that all adults with sickle cell disease undergo echocardiographic testing to identify if they are at risk for pulmonary hypertension and require treatment.
The primary symptom of pulmonary hypertension is shortness of breath, which is often severe. Pulmonary hypertension can be very serious and life threatening in the short- and long-term. If pulmonary hypertension develops suddenly it can cause respiratory failure, which is life threatening. Over time, pulmonary hypertension may cause a condition called cor pulmonale, in which the right side of the heart increases in size. In some cases, this enlargement can lead to heart failure.
After acute chest syndrome, stroke is the most common killer of patients with sickle cell disease who are older than 3 years old. Between 8 - 10% of patients suffer strokes, typically at about age 7. Patients may also suffer small strokes that may not be immediately noticeable. However, patients who have many of these small strokes may over time start behaving differently or have worsening mental functioning.
Strokes are usually caused by blockages of vessels carrying oxygen to the brain. Patients with sickle cell disease are also at high risk for stokes caused by aneurysm, a weakened blood vessel wall that can rupture and hemorrhage. Multiple aneurysms are common in sickle cell patients, but they are often located where they cannot be treated surgically.
Anemia is a significant characteristic in sickle cell disease (which is why the disease is commonly referred to as sickle cell anemia).
Severe worsening of anemia. Children, adolescents, and possibly young adults may experience what is called splenic sequestration. This happens when a large amount of the sickled red blood cells collect in the patient's spleen. Symptoms may include pain in the right abdomen below the ribs and a large mass (the swollen spleen) may be felt.
Chronic Anemia. Because of the short lifespan of the sickle red blood cells, the body is often unable to replace red blood cells as quickly as they are destroyed. This causes a particular form of anemia called hemolytic anemia. Most patients with sickle cell disease have a hemoglobin levels of 8 g/dL, much lower than people without sickle cell anemia. Chronic anemia reduces oxygen and increases the demand on the heart to pump more oxygen-bearing blood through the body. Eventually, this can cause the heart to become dangerously enlarged, with an increased risk for heart attack and heart failure.
On occasion, patients may experience what is called an aplastic crisis. This happens when the cells in the bone marrow that are normally trying to make new red blood cells suddenly stop working. This sudden stopping is often triggered by a virus called human parvovirus B19.
The kidneys are particularly susceptible to damage from the sickling process. Persistent injury can cause a number of kidney disorders, including infection. Problems with urination are very common, particularly uncontrolled urination during sleep. Patients may have blood in the urine, although this is usually mild and painless and resolves without damaging consequences. Kidney failure is a major danger in older patients and accounts for 10 - 15% of deaths in sickle cell patients. Renal medullary carcinoma is an aggressive, rapidly destructive tumor in the kidney that is rare but can occur as a result of sickle cell disease.
A reported 38 - 42% of males, including children, with sickle cell disease suffer from priapism. Priapism causes prolonged and painful erections that can last from several hours to days. If priapism is not treated, partial or complete erectile dysfunction can occur in 80% of cases.
Enlargement of the liver occurs in over half of sickle cell patients, and acute liver damage occurs in up to 10% of hospitalized patients. Because sickle cell patients often need transfusions, they have been at higher risk for viral hepatitis, an infection of the liver. This risk, however, has decreased since screening procedures for donated blood have been implemented.
About 30% of children with sickle cell disease have gallstones, and by age 30, 70% of patients have them. In most cases, gallstones do not cause symptoms for years. When symptoms develop, patients may feel overly full after meals, have pain in the upper right quadrant of the abdomen, or have nausea and vomiting. Acute attacks can be confused with a sickle cell crisis in the liver. Ultrasound is usually used to confirm a diagnosis of gallstones. If the patient does not have symptoms, no treatment is usually necessary. If there is recurrent or severe pain from gallstones, the gallbladder may need to be removed. Minimally invasive procedures (using laparoscopy) reduce possible complications. [For more information, see In-Depth Report #10: Gallstones.]
The spleen of most adults with sickle cell anemia is nonfunctional due to recurrent episodes of oxygen deprivation that eventually destroy it. Injury to spleen increases the risk for serious infection. Acute splenic sequestration crisis (sudden spleen enlargement) can occur when the spleen suddenly becomes enlarged from trapped blood.
In some children with sickle cell disease, excessive production of blood cells in the bone marrow causes bones to grow abnormally, resulting in long legs and arms or misshapen skulls. Sickling that blocks oxygen to the bone can also cause bone loss and pain. Sickling that affects the hands and feet of children causes a painful condition called hand-foot syndrome. A condition called avascular necrosis of the hip occurs in about half of adult sickle cell patients when oxygen deprivation causes tissue death in the bone. Eventually adult patients may require surgery to remove diseased and dead bone tissue. Joint replacement may be required in severe cases. X-rays are not very useful for detecting early disease in the bones. MRI may be important.
Leg sores and ulcers occur in up to 10% of sickle cell patients and usually affect patients older than 10 years.
Sickle cell disease can damage blood vessels in the eye and cause scarring and detachment of the retina, which can lead to blindness.
Women with sickle cell disease who become pregnant are at higher risk for complications such as miscarriage, premature birth, and low birth weight. Sickle cell disease symptoms often worsen during pregnancy and pain crises become more frequent. However, with careful prenatal care and monitoring, serious problems can be avoided. Maternal mortality rates have dropped significantly over the past decades. Most women with sickle cell disease can now anticipate favorable pregnancy outcomes.
Older children and adult patients with sickle cell are subject to other medical problems, including impaired physical development and gum disease. In severe cases, sickle cell disease can cause multiple organ failure.
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