Hemoglobin J Guantanamo [alpha 2 beta 2 128 (H6) Ala----Asp] in association with hemoglobin C and alpha-thalassemia in a family from Benin

The First Case of Hemoglobin J-Guantanamo Reported During HbA1c Measurement by High-Performance Liquid Chromatography at Moroccan Military Hospital Mohammed V

We present a 57-year-old woman with diabetes mellitus and no other known comorbidities. HbA1c measurement by high-performance liquid chromatography (HPLC) gave unquantified results and a supernumerary peak was detected on the chromatogram. A thorough exploration of the hemoglobin profile showed the presence of an unclassified variant. Alkaline pH capillary electrophoresis revealed the presence of an abnormal peak migrating at zone 11, comprising 40.1% of total hemoglobin. An abnormal band migrating between hemoglobin A and hemoglobin F was observed by acid gel electrophoresis. Sequencing of the β-globin gene confirmed the presence of a rare hemoglobin variant, hemoglobin J-Guantanamo (HBB:c.386C>A) in the heterozygous state, which was for the first time documented in Morocco. Through this report, we emphasize the importance of careful analysis of the HPLC chromatogram for the detection of possible hemoglobin variants in HbA1c measurement.

Hb Mont Saint Aignan [beta128(H6)Ala-->Pro]: a new unstable variant leading to chronic microcytic anemia

Hb Mont Saint-Aignan [beta128(H6)Ala-->Pro] is a mildly unstable variant, associated with hemolytic anemia, marked microcytosis and increased alpha/beta biosynthetic ratio (1.55 versus 1.1 +/- 0.1 in the control). The abnormal chain was isolated by selective precipitation with isopropanol and the structural modification determined by protein chemistry methods (reversed phase high performance liquid chromatography and mass spectrometry). Possible mechanisms underlying the beta(+)-thalassemia-like expression of this variant are discussed.

Hb Sitia [beta128(H6)Ala-->Val]: an unstable variant with a substitution in the alpha1beta1 interface

Hb Sitia [beta128(H6)Ala-->Val] was found in a Greek female with slightly reduced red blood cell indices. The abnormal hemoglobin was indistinguishable from Hb A by electrophoresis but eluted after Hb A on cation exchange high performance liquid chromatography. DNA sequence analysis revealed a GCT-->GTT mutation at codon 128, which is predicted to encode an Ala-->Val substitution. This was confirmed by mass spectrometry analyses of the beta-globin chain. Since alanine at beta128(H6) interacts with several amino acids of the alpha1beta1 contact, its replacement by a larger residue results in a mild instability of the molecule and slight modifications of the oxygen binding properties.

Hemoglobin Redondo [beta 92(F8) His----Asn]: an unstable hemoglobin variant associated with heme loss which occurs in two forms

Hb Redondo [beta 92(F8) His----Asn] illustrates how post-translational structural modifications may modify the phenotypic expression of an unstable hemoglobin. This variant was found in a Portuguese patient suffering from a chronic hemolytic anemia. The electrophoretic pattern demonstrated that it occurred in two forms, both being semi-hemoglobins: the fastest one migrating like HbS and the other like HbA2; after a few days of storage at 4 degrees C the intensity of the slowest Hb fraction decreased while that of the other increased proportionally. In both cases, the RP-HPLC analysis of the tryptic digest of the aminoethylated beta chains demonstrated the presence of an abnormal beta T10 peptide carrying a His----Asx substitution. Microsequence study of these two peptides demonstrated that the slowest abnormal Hb fraction had a beta 92 His----Asn substitution and the fastest a His----Asp at the same site. All these results suggest that the beta 92 His----Asn variant loses readily its heme group and that a deamidation occurs rapidly in vitro, yielding a beta 92 Asp semi-hemoglobin. The oxygen affinity of the patient's red blood cells was increased, leading to a stimulation of erythropoiesis and to a macrocytic hemolytic disease.

A new hemoglobin variant found during investigations of diabetes mellitus: Hb Pavie [alpha 135 (H18) Val----Glu]

Hb Pavie [alpha 135 (H18) Val----Glu], found during HbA1c measurement in a patient of Italian origin investigated for diabetes mellitus, exemplifies how the presence of an abnormal hemoglobin interferes with the measurement of glycated hemoglobin. This variant hemoglobin migrates as Hb A1c on polyacrylamide gel isoelectric focusing (IEF) and therefore hindered the estimation of glycated hemoglobin by this method. By ion-exchange high-performance liquid chromatography (IE-HPLC) Hb Pavie was eluted as a shoulder of the major component and the corresponding glycated fraction together with Hb A1b. Hb Pavie was purified in order to determine how its functional properties may modify red cell survival. The only functional abnormality observed was a slight decrease of the oxygen affinity, and therefore the total amount of glycated hemoglobin was not expected to be decreased by a shortening of the red cell survival.