Sickle-cell disease

Sickle-cell disease is a genetic disorder in which red blood cells may change shape under certain circumstances. This causes the cells to become stuck in capillaries which deprives the downstream tissues of oxygen and causes ischemia and infarction. The disease usually occurs in periodic painful attacks, eventually leading to damage of internal organs, stroke, or anemia, and usually resulting in decreased lifespan. It is common in people from countries with a high incidence of malaria, and especially in West Africa, or in descendents from those people.

Signs and symptoms

Patients have baseline anemia that varies in severity, with hemoglobin levels of 7-9 mg/dl typical. Often white blood cell counts are elevated simply due to marrow hyperactivity. Reticulocyte counts are elevated, reflecting new red blood cells replacing the rapidly cleared older cells - red blood cell life span is markedly reduced in this disease.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Vasoocclusive crises

Vasoocclusive crises are caused by sickled red blood cells that obstruct capillaries and restrict bloodflow to an organ, resulting in ischemia, pain, and organ damage.

Related Topics:
Ischemia - Pain

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Because of its narrow vessels and function in clearing defective red blood cells, the spleen is frequently affected. It is usually infarcted before the end of childhood in individuals suffering from sickle cell anemia. This autosplenectomy increases the risk of infection from encapsulated organisms; preventive antibiotics and vaccinations are recommended for those with such asplenia. Liver failure may also occur with time.

Related Topics:
Spleen - Infarcted - Autosplenectomy - Asplenia - Liver failure

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Bone is also a common target of vasoocclusive damage, especially when the bone is particularly weight-bearing. Such damage may result in avascular necrosis (especially of the femur) and bone deterioration. The pain experienced by sickle-cell patients is also due to the bone ischemia.

Related Topics:
Bone - Avascular necrosis - Femur

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A recognized type of sickle crisis is the acute chest crisis, a condition characterized by fever, chest pain, and pulmonary infiltrate on chest x-ray. Given that pneumonia and intra-pulmonary sickling can both produce these symptoms, the patient is treated for both conditions. Treatment consists of admission, oxygen, close monitoring, and intravenous antibiotics.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Other sickle-cell crises

• Aplastic crisis. An acute worsening of the patient's baseline anemia producing pallor, tachycardia, and fatigue. This crisis is triggered by parvovirus B19, which directly affects erythropoiesis (production of red blood cells). Reticulocyte counts drop dramatically during the illness and the rapid turnover of red cells leads to the drop in hemoglobin. Most patients can be managed supportively; some need blood transfusion.
• Splenic sequestration crisis. An acute, painful enlargement of the spleen. Management is supportive, sometimes with blood transfusion.

Complications

Sickle cell anaemia can lead to various complications, including:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Overwhelming post (auto)splenectomy infection - due to functional asplenia, caused by encapsulated organisms such as Streptococcus pneumoniae and Haemophilus influenzae. Daily penicillin prophylaxis is the most commonly used treatment during childhood with some hematologists continuing treatment indefinitely. Patients benefit today from routine vaccination for Haemophilus influenzae, Pneumococcus and Meningococcus.
• Stroke - progressive vascular narrowing (occlusion) can prevent oxygen from reaching the brain, leading to stroke; cerebral infarction occurs in children, and cerebral hemorrhage in adults.
• Cholelithiasis and cholecystitis (gallstones) - prolonged hemolysis may lead to excessive bilirubin production and precipitation, leading to gallstones
• Avascular necrosis (aseptic bone necrosis) of the hip
• Decreased immune reactions due to hyposplenism (malfunctioning of the spleen)
• Priapism and infarction of the penis (in men)
• Osteomyelitis (bacterial bone infection) - salmonella is noted much more commonly than in the general population, but staphylococcus is still the most common pathogen.
• Opioid addiction (see below)