ANSWER 40
This boy has sickle cell diseaseand presents with his first serious bony/chest crisis. Sickle cell
disease occurs mainly in African black populations and sporadically in the Mediterranean
and Middle East. Haemoglobin S differs from haemoglobin A by the substitution of valine for
glutamic acid at position 6 in the $-chain. Sickled cells have increased mechanical fragility
and a shortened survival leading to a haemolytic anaemia, and also can block small vessels
leading to tissue infarction. Sickle cell disease has a very variable clinical course due to a
combination of reasons including the haemoglobin F (HbF) level and socio-economic factors.
It usually presents in early childhood with anaemia and jaundice due to a chronic haemolytic
anaemia, or painful hands and feet with inflammation of the fingers due to dactylitis. This
patient is having a pulmonary crisis characterized by pleuritic chest pain, shortness of breath
and hypoxia. It is usually precipitated by dehydration or infection (in this case, a sore throat).
The principal differential diagnoses of a patient presenting with pleuritic pain and breath-
lessness are pneumonia, pneumothorax and pulmonary emboli.
- Thrombotic: causing generalized or localized bony pains, abdominal crises, chest
crises, neurological signs or priapism. - Aplastic crises: triggered by parvovirus infection.
- Haemolytic anaemia.
- Sequestration crises in children with rapid enlargement of the liver and spleen,
usually in young children. - Aseptic necrosis: often of the humeral or femoral heads.
- Renal failure due to renal medullary infarction or glomerular disease.
- Hyposplenism due to autoinfarction in childhood.
! Major potential complications of sickle cell disease
This patient should be admitted for rest, intravenous fluids, oxygen and adequate anal-
gesia. He has a low arterial pO 2 and appears cyanosed. Cyanosis is more difficult to detect
in the presence of anaemia. Infection should be treated with antibiotics. A blood film will
show sickled erythrocytes and elevated reticulocyte count. The definitive investigation is
haemoglobin electrophoresis which will demonstrate HbS, absent HbA and a variable HbF
level. Partial exchange transfusion may be needed to reduce the level of his sickle cells to
less than 30 per cent. He should be followed up by an expert sickle team since this has been
shown to reduce admissions and improve quality of care. He may benefit from long-term
hydroxyurea which raises the HbF level and reduces the number of crises.
- In African-Caribbean patients, sickle cell disease should be thought of as a cause of
chest or abdominal pain. - Patients with sickle cell disease should be looked after in specialized haematology units
with psychological support available. - Severe thrombotic complications should be treated with partial exchange transfusion.