The unstable haemoglobin haemolytic anaemias result from the presence in the red cell of a
structurally abnormal haemoglobin variant. There are many mutations producing unstable
haemoglobins; most are single amino acid replacements that affect a few key areas of the
haemoglobin structure. A wide range of haemoglobin instability is evident from in vitro
studies, extending from mutants with a subclinical degree of instability to those associated
with severe haemolytic disease. The characteristic feature of variants associated with …