Hb Montreal II: a novel elongated beta-globin variant caused by a frameshift mutation [beta142 (-C)].

We report a novel elongated C-terminal beta hemoglobin (Hb) variant caused by a single nucleotide (C) deletion at codon 143 (nucleotide 480 of GenBank entry NM_000518). This deletion leads to the substitution of histidine 143 by threonine, and displaces the beta Hb gene stop codon from codon 147 to codon 157. It was identified in a 30-year-old man from Montreal, and called Hb Montreal II. This Hb variant differs from its normal counterpart by 14 residues, the latter 10 being identical to those observed in Hbs Tak, Cranston, Saverne, Trento, and Florida. The patient did not present thalassemic features but had a compensated chronic hemolysis with splenomegaly, red cell inclusion bodies, and a positive Kleihauer test.