Hemoglobin Variant (Hemoglobin Aalborg) Mimicking Interstitial Pulmonary Disease

Hemoglobin Aalborg is a moderately unstable hemoglobin variant with no affiliation to serious hematological abnormality or major clinical symptoms under normal circumstances. Our index person was a healthy woman of 58, not previously diagnosed with hemoglobinopathy Aalborg, who developed acute respiratory failure after a routine cholecystectomy. Initially she was suspected of idiopathic interstitial lung disease, yet a series of tests uncovered various abnormal physiological parameters and set the diagnosis of hemoglobinopathy Aalborg. This led us to examine a group of the index person’s relatives known with hemoglobinopathy Aalborg in order to study whether the same physiological abnormalities would be reencountered. They were all subjected to spirometry and body plethysmography, six-minute walking test, pulse oximetry, and arterial blood gas samples before and after the walking test. The entire study population presented the same physiological anomalies: reduction in diffusion capacity, and abnormalities in and p50 values; the latter could not be presented by the arterial blood gas analyzer; furthermore there was concordance between pulse oximetry and arterial blood gas samples regarding saturation. These data suggest that, based upon the above mentioned anomalies in physiological parameters, the diagnosis of hemoglobinopathy Aalborg should be considered. 1. Introduction Unstable hemoglobinopathies (Hb) are a rare disease entity of mutational events in the hemoglobin which are characterized by substitutions in the primary sequence of the globin [1]. These mutations alter the tertiary or quaternary structure of the molecule and therefore cause destabilization of the hemoglobin tetramer. A wide range of hemoglobin instabilities are known from in vitro studies, and the clinical findings span from subclinical cases to cases with severe hemolytic disease, for example, beta-thalassemia major or sickle cell disease [2]. Hb present with a broad spectrum of clinical manifestations; however, patients often have very few symptoms apart from slight fatigue, because the hemoglobin is often stable under clinically stable conditions [1–4]. Hemoglobin Aalborg is a rare, unstable hemoglobin variant where a glycine residue (E18) is replaced by arginine (β74(E18)Gly->Arg). The incidence and prevalence of Hb Aalborg are not known. It has a reduced oxygen affinity, both in the absence and in the presence of organic phosphates, and a raised oxygen affinity for organic phosphates, despite the fact that the replaced amino acid residue is too far from the heme to affect it