Hb Vila Real [beta36(C2)Pro®His] in Italy: characterization of the amino acid substitution and the DNA mutation

A rare high oxygen affinity hemoglobin variant was identified in a 22-year-old male patient from Napoli (Naples, Italy) affected by erythrocytosis. A detailed structural characterization of the variant hemoglobin was carried out, both at the protein and DNA levels essentially by mass spectrometric procedures and allele-specific amplification techniques. The amino acid substitution was determined by liquid chromatography tandem mass spectrometric analysis of the tryptic digest as β36(C2)Pro → His; the corresponding DNA mutation was identified as C → A at the second position of codon 36 of the β chain (CCT → CAT). These variations identified the presence of Hb Vila Real, described only once before in a Portuguese woman. Haplotype analysis of DNA polymorphisms showed that the β-globin gene of Hb Vila Real was associated with haplotype I.