Hemoglobin J-Guantanamo [alpha 2 beta 2 128(H6)Ala----Asp] found in a Chinese family

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.

Unstable hemoglobins

About 70 variants of Hb A with associated hemolytic disorders have been reported during the past 30 years. I have classified them according to four grades of severity of chronic hemolysis. Acute episodes of severe hemolysis may be seen in all classes. In addition, some 80 variants without overt hemolysis have given positive results with in vitro hemoglobin instability tests. The stereochemical bases for instability can be conjectured in most cases, although few unstable hemoglobins have actually been studied by X-ray crystallography. The mechanisms for denaturation of normal Hb A and its acceleration in unstable hemoglobins were proposed some 15 years ago. The alterations of membrane lipids and proteins leading to red cell senescence and the relevance of hemoglobin denaturation to this process are presently being investigated. Several "hyperunstable" variants are clinically silent, or equivalent to a thalassemia, probably because of very efficient degradation of the abnormal chains.