Hb Trento: an elongated C-terminal beta chain due to a new frameshift mutation [beta144 (-A)]

An elongated C-terminal hemoglobin variant, due to the deletion of nucleotide A in codon 144 (nucleotide 63600 GenBank entry UO1317) was found in a 31-year-old woman from Trento (northeastern Italy). This deletion led to the replacement of lysine at beta144 by a serine residue, the disappearance of the stop codon at position 147, and the presence of 12 additional residues, identical to those observed in Hbs Saveme, Tak and Cranston, which result from a similar mechanism. Hb Trento, amounting to 29% of the total hemoglobin, was unstable and had, as the other variants of this group, an increased oxygen affinity. It led to a mild compensated hemolytic anemia with red cell inclusion bodies. Functional studies of the isolated abnormal hemoglobin were difficult to perform because of autoxidation, precipitation, and formation of hybrids with Hb A.