Sickle Cell (Vaso-Occlusive) Crisis
The hallmark complication of sickle cell disease is the sickle cell crisis (also called vaso-occlusive crisis), which is a sudden and severe episode of pain. These crises occur when sickled cells block the flow of blood through the body.
The pattern of a sickle cell crisis may occur as follows:
- In general, any activity that boosts the body's requirement for oxygen, such as illness, physical stress, or being at high altitudes, increases the risk for a sickle pain crisis. Very often, however, the trigger is unknown.
- Patients typically describe the pain as sharp, intense, and throbbing. Severe sickle cell pain is described as comparable to cancer pain, and more severe than postsurgical pain. Shortness of breath is common.
- Pain most commonly occurs in the chest, arms, legs, lower back, or stomach, and can migrate from one location to another. Episodes usually recur in the same areas. Attacks can last anywhere from several hours to several days. In some cases, the patient may need to stay in the hospital.
- When a large number of sickled red blood cells collect and pool in the patient's spleen, a condition called splenic sequestration can occur. The spleen becomes enlarged and swollen, causing pain and leading to anemia. Repeated episodes of splenic sequestration can cause scarring and permanent damage to the spleen. Sickle cell crises can also occur in and damage the liver.
- Males of any age may have prolonged, often painful erections, a condition called priapism.
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.
Acute Chest Syndrome (ACS)
Acute chest syndrome (ACS) is a sudden condition that occurs when the lung tissues are deprived of oxygen. ACS can occur when:
- Sickle blood cells block blood vessels in the lungs during a sickle cell crisis.
- Fat embolisms (clots), which are particles formed from fatty tissue in the bone marrow, block small blood vessels and arteries of the lungs.
- Infections such as pneumonia cause problems with lung function.
ACS can be very painful, dangerous, and even life threatening. Once ACS occurs, it is likely to happen again. ACS is a leading cause of illness among patients with sickle cell disease. Children with asthma are at particular risk for having ACS.
Symptoms of ACS include:
- Fever of 101.3 °F degrees (38.5 °C) or above
- Rapid or labored breathing
- Wheezing or cough
- Chest pain
- Back or stomach pain
Infections are common and an important cause of severe complications. Before early screening for sickle cell disease and the use of preventive antibiotics in children, many infants with sickle cell died from infections. Fortunately, the use of required sickle cell screening tests for newborns, and the use of preventive antibiotics and immunizations in babies who are born with the disease, have significantly reduced mortality rates.
Infections in Infants and Toddlers with Sickle Cell Disease. The most common organisms causing infection in children with sickle cell disease include:
Streptococcus pneumoniae (can cause pneumonia, blood infections, or meningitis)
Haemophilus influenzae (also a cause of pneumonia, blood infections, and meningitis)
Such infections pose a serious threat to infants and very young children with sickle cell disease. They can rapidly progress to fatal pneumonia in infants, and death can occur within 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:
Chlamydia pneumoniae and Mycoplasma pneumoniae. These are the important infections in acute chest syndrome (see above).
- Gram-negative bacteria. This group of bacteria mostly infects hospitalized patients and can cause serious pneumonias and other infections.
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 a significant cause of death in sickle cell disease. Many doctors recommend that all adults with sickle cell disease have echocardiographic testing to identify if they are at risk for pulmonary hypertension and need 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). People with sickle cell disease have a chronic shortage of healthy red blood cells, which leads to persistent anemia.
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 hemoglobin levels of about 8 g/dL, much lower than hemoglobin levels in healthy people. Chronic anemia reduces oxygen levels and increases the demand on the heart to pump more oxygen-bearing blood through the body. Eventually, this can cause the heart to enlarge dangerously, with an increased risk for heart attack and heart failure.
Aplastic Crisis. Sometimes patients may experience 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 and are unable to form new red cells. This leads to a sudden drop in the red blood cell count (hemoglobin level). This sudden stopping is often triggered by a virus called human parvovirus B19.
Splenic Sequestration. Children, adolescents, and possibly young adults may experience splenic sequestration, which can be a life-threatening condition. This happens when a large number of sickled red blood cells collect in the patient's spleen. In addition to pain and abdominal swelling, splenic sequestration can cause a sudden drop in hemoglobin levels.
Many males with sickle cell disease, including children, suffer from priapism. Priapism causes prolonged and painful erections that can last from several hours to days. If priapism is not treated, permanent partial or complete erectile dysfunction can occur.
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 in association with sickle cell disease.
Enlargement of the liver (hepatomegaly) occurs in many sickle cell patients, which can lead to permanent liver damage and failure. In addition, because sickle cell patients often need blood transfusions, they are at higher risk for acquiring hepatitis C. This risk, however, has decreased since screening procedures for donated blood have been implemented.
Gallstones are a common complication of sickle cell disease. 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, usually no treatment is necessary. If there is recurrent or severe pain from gallstones, the gallbladder may need to be removed.
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 enlarges as a result of trapped blood.
Bone and Joint Problems
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 adult sickle cell patients when oxygen deprivation causes tissue death in the bone. Eventually adult patients may need surgery to remove diseased and dead bone tissue. Patients with severe cases may need joint replacement.
Leg Sores and Ulcers
Leg sores and ulcers may occur. They 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.
Pregnancy and Sickle Cell Disease
Women with sickle cell disease who become pregnant are at higher risk for complications such as miscarriage and premature birth, and their babies may have 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.
Other Medical Complications
Older children and adult patients with sickle cell are subject to other medical problems, including delayed growth and physical development. In severe cases, sickle cell disease can cause multiple organ failure.