Sickle cell anaemia is characterised by periods of good health with intervening crises

A number of types of crises are recognised:

• thrombotic, 'vaso-occlusive', 'painful crises'
• acute chest syndrome
• anaemic
  • aplastic
  • sequestration
• infection

Thrombotic crises

• also known as painful crises or vaso-occlusive crises
• precipitated by infection, dehydration, deoxygenation (e.g. high altitude)
• painful vaso-occlusive crises should be diagnosed clinically - there isn't one test that can confirm them although tests may be done to exclude other complications
• infarcts occur in various organs including the bones (e.g. avascular necrosis of hip, hand-foot syndrome in children, lungs, spleen and brain

Acute chest syndrome

• vaso-occlusion within the pulmonary microvasculature → infarction in the lung parenchyma
• dyspnoea, chest pain, pulmonary infiltrates on chest x-ray, low pO2
• management
  • pain relief
  • respiratory support e.g. oxygen therapy
  • antibiotics: infection may precipitate acute chest syndrome and the clinical findings (respiratory symptoms with pulmonary infiltrates) can be difficult to distinguish from pneumonia
  • transfusion: improves oxygenation
• the most common cause of death after childhood

Aplastic crises

• caused by infection with parvovirus
• sudden fall in haemoglobin
• bone marrow suppression causes a reduced reticulocyte count