J. Sanchez

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.