Sickle cell crisis (episodes of pain): Episodes of pain during a sickle cell crisis are one of the most common and upsetting symptoms of sickle cell anaemia.
A sickle cell crisis is triggered when the abnormal blood cells block the small blood vessels that supply the body’s tissue. This causes the cells in the affected tissue to start dying, resulting in swelling which irritates nearby nerve endings.
People with sickle cell anaemia have also reported that the pain can take many different forms. For example, it can be an aching, throbbing pain, a sharp, shooting pain, or a penetrating, burning pain.The symptoms of pain can range from moderate to severe, and episodes can last from several hours to several weeks.
A sickle cell crisis can often occur for no apparent reason, although certain factors can trigger a crisis, such as the cold, dehydration, infections (particularly those that cause high temperatures or breathing difficulties), the body suddenly becoming short of oxygen as a result of exercise, sudden exertion or stress.
Definition from NHS Choices: (sickle-cell) crisis