Tetralogy of Fallot with hypoxemia in a patient with beta thalassemia intermedia.

Abstract The presence of cyanotic congenital heart disease in a 12 year old child with a moderately severe beta thalassemia syndrome demonstrated the effect of severe hypoxemia on red cell production in this disorder. Family studies suggested that the patient was a double heterozygote, inheriting two beta thalassemia genes of different severity. A right to left intracardiac shunt caused pronounced arterial desaturation and increased erythropoietin 100-fold. Plasma iron turnover was accelerated, but less than 10 per cent of injected radioiron was incorporated into circulating red blood cells. Oxygen delivery to peripheral tissues was accomplished by a high cardiac output and a relatively high hemoglobin level to compensate for arterial desaturation. After operative correction of the right to left shunt, arterial saturation became normal. Oxygen delivery was maintained despite the development of moderate anemia and lower cardiac output. Erythropoietin decreased 30-fold and plasma iron turnover decreased sevenfold whereas erythropoiesis became much more effective. Despite this, the measured deficiency in the synthesis of beta globin relative to alpha globulin was greater after surgery. In addition, hemoglobin F increased from 9.5 per cent to 25 per cent of the total circulating hemoglobin after correction of the hypoxemia.