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Sickle cell trait, sickle cell disease, Hemoglobin La Desirade, unstable hemoglobin variant, alpha thalassemia
Hemoglobin La Desirade (Hb La Desirade) is an unstable hemoglobin variant characterized by amino acid Alanine (Ala) replacing Valine (Val) at position 129 (H7) in the beta chain. Hb La Desirade exhibits a decreased oxygen affinity and normal heme-heme interaction. Interestingly, on analysis by standard electrophoresis, it migrates in the same region as normal HbA, and HbA actually represents a combination of HbA and Hb La Desirade together. This variant was reported as compound heterozygous with other Hemoglobin variants such as HbS, HbC or beta thalassemia, and more recently with Southeast Asian ovalocytosis and Hb Louisville with varying clinical manifestations. Herein, we describe the clinical and laboratory findings in a number of Omani Arab families who presented to our service for various reasons, presenting with Hemoglobin La Desirade with sickle gene and alpha thalassemia. Our patients with Hb La Desirade trait, were clinically asymptomatic with no evidence of anemia. However when it is associated with other abnormal hemoglobin variants such as HbS, leading to sickle/La Desirade compound heterozygosity, there was mild anemia with significant degree of hypochromia and microcytosis. The most striking feature was that the levels of HbS and HbA were almost equal on HPLC, and these cases could be misdiagnosed as sickle cell trait (SCT). However, the levels of Hb S in these compound heterozygotes (40.4-45.9) were higher than normally seen for the diagnosis of SCT in this population.
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