Coexisting hereditary methaemoglobinaemia and heterozygous beta-thalassaemia

Cyanosis was noted within a few weeks after birth in two sisters. On investigation the cause of cyanosis was found to be congenital methaemoglobinaemia due to NADH diaphorase deficiency. Heterozygous beta-thalassaemia was present as an additional incidental finding in one of the sisters, but did not contribute to the symptoms, thus showing that the two diseases, when coexistent, do not pose additional haematological problems. However, it is possible that the beta-thalassaemia counteracts the tendency to compensatory erythrocytosis induced by methaemoglobinaemia.