A the Bone Changes in Sickle Cell Anaemia

heterozygous and homozygous states to explain the symptomless sickle cell trait and the true sickle cell anaemia. An individual receiving the haemoglobin S gene from one parent only (the heterozygous state A/S) would have the sickle cell trait, whereas if the gene should be received from both parents (the homozygous state 5/5) he would have sickle cell anaemia (Fig. I). Sickle cell anaemia and its variants-In sickle cell anaemia the greater part of the haemoglobin is of the S type but there is a small fraction of foetal or F haemoglobin which is resistant to denaturation with alkali. Under reduced oxygen tension, the S haemoglobin comes out of solution and the resulting “ crystallisation “ produces the bizarre, sickle-shaped red cells. In the arterial blood, only about 5 per cent of the erythrocytes are sickle-shaped. whereas after prolonged exposure to low oxygen tension, 90 to 100 per cent become so. These cells may block capillaries, venules or even arterioles. If an area of skin affected by this process is examined, a tangled mass of these cells will be found held together in a loose fibrin mesh. In poorly vascularised areas, such as the lower leg, this may cause chronic ulceration (Murphy and Shapiro 1945). In the sickle cell trait, less than half the haemoglobin is of the S type, the remainder being normal or type A. The sickle cell trait is usually a benign condition, but in certain circumstances (such as flight in an unpressurised aircraft) symptoms may occur. Smith and Conley (1955) described fourteen cases of splenic infarction in patients of this kind. In 1951 Itano described a second haemoglobin variant (C), which can interact with haemoglobin S to produce sickle cell haemoglobin C disease (SIC). This condition is clinically milder than sickle cell anaemia and is less commonly associated with crises, but there is a peculiar tendency to avascular necrosis of epiphyses. Smith and Conley (1954) went so far as to suggest that avascular necrosis of bone occurred only in the variants of sickle cell disease and never in homozygous sickle cell anaemia; but Tanaka, Clifford and Axelrod (1956) and Carrington. Ferguson and Scott (1958) showed that similar changes may be found in true sickle cell anaemia and described eight cases proved by electrophoresis. We have been able to confirm and extend their findings. The S gene is found in I0’9 per cent of Jamaicans (Went 1957). Haemoglobin C is the next commonest variant and is found in 3 1 per cent of Jamaicans. The thalassaemia gene is also found in Jamaica. In addition to five cases of thalassaemia major. we have seen eleven cases of sickle cell thalassaemia disease. This condition needs special consideration, because with the normal haematological techniques and with paper electrophoresis it may be impossible to distinguish it from true sickle cell anaemia. Two of the cases of sickle cell thalassaemia disease which we have encountered were in Afro-Chinese