Sickle cells

Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia (SCA). It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blood cells. This leads to a rigid, sickle-like shape under certain circumstances. Problems in sickle cell disease typically begin around 5 to 6 months of age. A number of health problems may develop, such as attacks of pain ('sickle cell crisis'), anemia, swelling in the hands and feet, bacterial infections and stroke. Long-term pain may develop as people get older. The average life expectancy in the developed world is 40 to 60 years. Sickle cell disease occurs when a person inherits two abnormal copies of the haemoglobin gene, one from each parent. This gene occurs in chromosome 11. Several subtypes exist, depending on the exact mutation in each haemoglobin gene. An attack can be set off by temperature changes, stress, dehydration and high altitude. A person with a single abnormal copy does not usually have symptoms and is said to have sickle cell trait. Such people are also referred to as carriers. Diagnosis is by a blood test, and some countries test all babies at birth for the disease. Diagnosis is also possible during pregnancy. The care of people with sickle cell disease may include infection prevention with vaccination and antibiotics, high fluid intake, folic acid supplementation and pain medication. Other measures may include blood transfusion and the medication hydroxycarbamide (hydroxyurea). A small percentage of people can be cured by a transplant of bone marrow cells. As of 2015, about 4.4 million people have sickle cell disease, while an additional 43 million have sickle cell trait. About 80% of sickle cell disease cases are believed to occur in Sub-Saharan Africa. It also occurs relatively frequently in parts of India, the Arabian Peninsula and among people of African origin living in other parts of the world. In 2015, it resulted in about 114,800 deaths. The condition was first described in the medical literature by the American physician James B. Herrick in 1910. In 1949, the genetic transmission was determined by E. A. Beet and J. V. Neel. In 1954, the protective effect against malaria of sickle cell trait was described. Signs of sickle cell disease usually begin in early childhood. The severity of symptoms can vary from person to person. Sickle cell disease may lead to various acute and chronic complications, several of which have a high mortality rate. The terms 'sickle cell crisis' or 'sickling crisis' may be used to describe several independent acute conditions occurring in patients with SCD. SCD results in anaemia and crises that could be of many types including the vaso-occlusive crisis, aplastic crisis, sequestration crisis, haemolytic crisis, and others. Most episodes of sickle cell crises last between five and seven days. 'Although infection, dehydration, and acidosis (all of which favor sickling) can act as triggers, in most instances, no predisposing cause is identified.' The vaso-occlusive crisis is caused by sickle-shaped red blood cells that obstruct capillaries and restrict blood flow to an organ resulting in ischaemia, pain, necrosis, and often organ damage. The frequency, severity, and duration of these crises vary considerably. Painful crises are treated with hydration, analgesics, and blood transfusion; pain management requires opioid administration at regular intervals until the crisis has settled. For milder crises, a subgroup of patients manage on nonsteroidal anti-inflammatory drugs (NSAIDs) such as diclofenac or naproxen. For more severe crises, most patients require inpatient management for intravenous opioids; patient-controlled analgesia devices are commonly used in this setting. Vaso-occlusive crisis involving organs such as the penis or lungs are considered an emergency and treated with red-blood cell transfusions. Incentive spirometry, a technique to encourage deep breathing to minimise the development of atelectasis, is recommended. 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 anaemia. This spleen damage increases the risk of infection from encapsulated organisms; preventive antibiotics and vaccinations are recommended for those lacking proper spleen function.