Hb S-San Martin: a new sickling hemoglobin with two amino acid substitutions [ß6(A3)Glu→Val;ß105(G7)Leu→Pro] in an Argentinean family.

A new sickling hemoglobin (Hb) detected in an Argentinean family from San Martín, Buenos Aires, Argentina, is hereby described. Two mutations were identified on the same ß-globin gene resulting in a new variant named Hb San Martin. One mutation was found on exon 1, corresponding to Hb S [ß6Glu→Val, GAG>GTG] and the second one on exon 3 at ß105(G7)Leu→Pro, CTC>CCC. The replacement of leucine by proline will likely impair the structure breaking helix G and causing instability of the molecule and the clinical manifestations typical of unstable Hbs. The mutation at ß105 seemed to be a de novo one in our patients, arising on a previously mutated gene, due to the fact that Hb S is the most frequent structural variant.