ABSTRACT
This is a case of sickle cell anaemia with dactylitis induced by low temperatures. The infection the week before may have been secondary to erythrovirus (formally known as parvovirus), which can cause an aplastic crisis (a reduction or total absence of haematopoietic cell lines of the marrow, leading to pancytopenia). Sickle cell disease is a homozygous inheritance of faulty β-globin genes that is most common in African, Mediterranean and Middle-Eastern countries. A single amino acid substitution ( glutamine → valine) results in an abnormal haemoglobin that becomes insoluble in its deoxygenated state and causes sickling ( crescentic shaping) of red blood cells. Sickled cells can become trapped in the microcirculation, leading to thrombosis and ischaemia. Such vasoocclusive crises include dactylitis (swelling and pain in the digits) and priapism (prolonged erection). Management of acute painful crises is by analgesia, warmth and rehydration. Diagnosis of sickle cell disease can be made by several methods: blood film appearance, haemoglobin electrophoresis or using screening methods in which the blood is deoxygenated to induce sickling. Electrophoresis has two general applications. The first is the diagnosis of haemaglobinopathies, including sickle cell disease, by separating the abnormal haemoglobins at an alkaline pH. The second is in the investigation of myeloma to detect monoclonal immunoglobulins characteristic of the disease.
