Hb Chile [β28(B10)Leu→Met]: An unstable hemoglobin associated with chronic methemoglobinemia and sulfonamide or methylene blue-induced hemolytic anemia

Among the causes of life-long cyanosis are congenital methemoglobinemia due to M hemoglobins, congenital methemogiobinemia due to methemoglobin reductase deficiency, a small number of low oxygen affinity hemoglobins, and a small number of unstable hemoglobins that spontaneously form methemoglobin in vivo at an accelerated rate. We report an unstable hemoglobin with these characteristics that was observed in a family of indigenous (native American) origin living near Santiago, Chile. This variant has the substitution β28(B10)Leu→Met, unambiguously corresponding to the DNA mutation of CTG→ATG in β-globin gene codon 28.