Erythraemia due to haemoglobin San Diego

Secondary erythrocytosis due to hemoglobin San Diego

High-oxygen-affinity hemoglobin variants are a rare clinical entity that can present with secondary erythrocytosis. Herein, the author reports a case of a 41-year-old man with a 4-year history of secondary erythrocytosis of unknown etiology. Physical examination was unremarkable except for plethora of the palms. Myeloproliferative neoplasms and common causes of secondary erythrocytosis were ruled out. The P50 oxygen-hemoglobin dissociation curve was left shifted. Hemoglobin electrophoresis was silent; however, globin mass spectrometry revealed a β-globin variant. Globin sequencing confirmed hemoglobin San Diego. This case highlights the fact that rare high-oxygen-affinity variants should be considered in the differential diagnoses of secondary erythrocytosis.

Hemoglobin San Diego/beta zero thalassemia in a Greek adult

Interaction of beta zero thalassemia with Hb San Diego [a high affinity hemoglobin variant, alpha 2 beta (2)109(G11)Val----Met] in a 29-year-old Greek male is described. A marked polycythemia with low MCH and MCV, but minor clinical problems were observed. Functional properties of the isolated variant are described.

Tryptic hydrolysis at asparagine residues in globin chains

Commercially available Tos-PheCH2Cl-treated or untreated bovine trypsin (EC 3.4.21.4) is shown to catalyse minor tryptic hydrolysis at the carboxyl side of asparagine residues in globin chains. This activity is not removed by the purification of enzyme, using CM-cellulose chromatography and subsequent affinity chromatography on trypsin inhibitor columns, neither is it inhibited by Tos-PheCH2Cl treatment of the CM-cellulose purified enzyme. It is suggested that the ability to hydrolyse globin chains at asparagine residues may represent an inherent feature of the trypsin molecule.