Clinical features
There is much variation in the clinical presentation and course of sickle cell anaemia, and the way in which it affects different individuals. In some the abnormality of the blood has few adverse effects and the diagnosis is made by chance during routine blood tests. Other people have mild to moderate anaemia but function normally most of the time with infrequent ill health. Others experience frequent painful crises, have debilitating anaemia and develop serious complications.
The clinical features are described under a number of headings -:
Acute effects of a crisis
Sickle cell crises cause episodes of pain affecting the abdomen, chest, back and limbs accompanied by fever, vomiting and malaise. The pain may be severe, the person is unwell, they may have jaundice and are confined to bed for a few days. During the crisis the person tends to become more anaemic than usual. Some people may develop severe anaemia of rapid onset such that an emergency blood transfusion is needed.
People with sickle cell anaemia are prone to infections, and crises may be precipitated by a minor infection such as a cold. Infections may rapidly become severe leading to pneumonia, meningitis, osteomyelitis or septicaemia (generalised blood poisoning). These infections may be life threatening.
Sudden and severe damage to the lungs may occur during a crisis and the body is unable to receive sufficient oxygen. This is known as an acute chest syndrome and presents with fever, chest pain and shortness of breath. Acute chest syndrome is a major cause of sudden death, especially in younger age groups
The nervous system may be affected during a crisis leading to seizures, bleeding into the brain (cerebral haemorrhage) or stroke. Children are at highest risk of stroke, around 8% of children with sickle cell will have had a stroke. High risk children can be identified using transcranial Doppler screening (ultrasound of the blood vessels in the brain). Those at highest risk are put on a blood transfusion programme and this reduces the risk of a stroke happening. Those on a regular transfusion programme will develop the problems of iron overload if not treated prophylactically with iron chelation therapy.
About 20% of adults with sickle cell have evidence of silent infarcts (signs of a stroke on scanning but symptoms not recognised at the time) this group have evidence of impaired cognitive function on testing.
Sickle retinopathy is caused by bleeding into the retina; the symptom of this is sudden onset blindness.
Between crises
In many individuals the symptoms of the crisis resolve with appropriate treatment and the person returns to normal after seven to ten days. Some people are persistently anaemic between crises with haemoglobin levels between 50 – 70% of normal. (Normal haemoglobin level 11 – 13 g/dl). In some individuals this will cause few symptoms because their body has become adapted to functioning with reduced haemoglobin; in others it will cause fatigue and shortness of breath on exertion. Over the years people who have frequent crises, and people with more severe anaemia, will generally experience poorer health overall. They are also more likely to develop long-term disabling complications.
Long-term complications
- The head of the femur (thigh bone) that forms part of the hip joint may undergo severe damage (avascular necrosis) in sickling crises. The hip joint becomes very painful on movement and ultimately severe arthritis of the hip develops. Joint movement will become very restricted and walking is limited. Avascular necrosis may also occur in the shoulder joint causing pain, deformity and restricted upper limb function. Severe arthritis of the hip or shoulder joint occurs at a relatively young age, and the joint requires artificial replacement.
- Abnormalities of the spleen occur. One of the roles of the spleen is to remove red cells, which have a normal life span of about 120 days, from the circulation. In sickle cell anaemia excessive numbers of sickled cells accumulate in the spleen causing enlargement of the organ in childhood. Ultimately the normal structure of the spleen is affected, it shrinks in size and its functions become impaired. The normal spleen plays a role in protecting the body against infection. As a result the person with sickle cell anaemia is more prone to infections and more likely to develop serious infections.
- Persistent skin ulcers may develop on the lower legs that fail to heal fully despite treatment.
- Repeated damage to the lungs leads to chronic pulmonary hypertension, a condition that causes progressive shortness of breath and may lead to heart failure.
- Over the years permanent damage to the blood supply of the kidneys causes impaired renal function that may lead to renal failure.
- Cognitive impairment related to silent infarcts is present in 20% of adults with sickle cell.
- Blindness may result from bilateral sickle retinopathy.
- Problems of iron overload related to regular transfusion treatment.
Click on the link for details of:
Amended May 2009
