Hb Johnstown [β109 (G11) Val→Leu]: Second case described and associated for the first time with β0‐thalassemia in two Spanish families

Hb Johnstown, a high oxygen affinity hemoglobin, was identified in four members from two unrelated Spanish families with erythrocytosis and left-shifted hemoglobin–oxygen dissociation curve. This hemoglobin variant, electrophoretically silent, was analyzed by reverse-phase high-performance liquid chromatography, and the mutation was characterized at the DNA level by β gene sequencing. In one of these families, two members are affected with Hb Johnstown in association with β0-thalassemia. In these cases the erythrocytosis and low values for P50 due to Hb Johnstown remain in spite of the β-thalassemia. Am. J. Hematol. 65:298–301, 2000. © 2000 Wiley-Liss, Inc.