[The unstable hemoglobin disease].

The unstable hemoglobin disease result from the presence of a structurally abnormal hemoglobin variant with substitution or deletion of amino acid in the red cell. Characteristic of the unstable hemoglobin disease is the presence of inclusions of precipitated denatured hemoglobin called Heinz bodies in the red cells. Almost 200 unstable hemoglobins have now been identified. Hundred of these hemoglobins arise hemolysis or abnormal oxygen affinity, and another 100 hemoglobins have no hematological abnormalities but with instability on in vitro test. The inheritance pattern of the unstable hemoglobin is autosomal dominant. The most common causes of instability re amino acid substitutions that disrupt the alpha-helix of globin or alter the steric configuration of the hem pocket by the insertion of polar amino acid in the interior of the hemoglobin molecule, or deletion of amino acid in the helix. The unstable hemoglobins have a greater tendency to be spontaneously oxidized to methemoglobin with subsequent formation of hemichromes and precipitations.