Hemoglobin Rambam (β69[E13]Gly→Asp), a pitfall in the assessment of diabetic control: characterization by electrospray mass spectrometry and HPLC

Abstract

Abstract Hemoglobin (Hb) Rambam, or β69[E13]Gly→Asp, has been identified in a German woman also suffering from non-insulin-dependent diabetes mellitus and chronic obstructive pulmonary disease. This is the first observation of this Hb variant in a German family thus far. The detailed evaluation of its structure using electrospray mass spectrometry revealed new minor glycohemoglobin components and showed that the attachment of glucose to the β NH2 terminus occurred at an almost identical rate in both wild-type and mutant β-chains. However, the introduction of a carboxyl group at β69 seems to increase the glycation of ε-amino groups of lysine residues. The glycemic state in the propositus was well reflected by the total glycohemoglobin concentrations but not by the Hb A1C values, which did not reflect hemoglobin glycation in this patient. This case demonstrates that Hb A1C cannot be used reliably in the management of diabetic patients carrying Hb variants such as Hb Rambam. Functional studies of the whole blood of the heterozygous carrier demonstrated extremely low oxygen affinity, which may have been caused by increased 2,3-diphosphoglycerate related to chronic obstructive pulmonary disease and hyperthyroidism. None of the clinical symptoms could be directly associated to Hb Rambam.