Hb Mont Saint Aignan [beta128(H6)Ala-->Pro]: a new unstable variant leading to chronic microcytic anemia

Hb Mont Saint-Aignan [beta128(H6)Ala-->Pro] is a mildly unstable variant, associated with hemolytic anemia, marked microcytosis and increased alpha/beta biosynthetic ratio (1.55 versus 1.1 +/- 0.1 in the control). The abnormal chain was isolated by selective precipitation with isopropanol and the structural modification determined by protein chemistry methods (reversed phase high performance liquid chromatography and mass spectrometry). Possible mechanisms underlying the beta(+)-thalassemia-like expression of this variant are discussed.