Hemoglobin S/OARAB: Thirteen new cases and review of the literature

Hemoglobin variants identified in the Uganda Sickle Surveillance Study

“…24 Heterozygotes are asymptomatic with mild microcytosis and anemia, but disease manifestations may occur when coinherited with Hb S, Hb C, or b-thalassemia. 25,26 Individuals who are homozygous for Hb O-Arab may have mild microcytic anemia, although those with symptomatic recurrent anemia and jaundice have been described. 25,27 Hb Kenya accounted for 27% of all variants and predominates in the eastern regions of Uganda.…”

A Patient with a Previous Diagnosis of Hemoglobin S/C Disease with an Unusually Severe Disease Course

“…Hb O Arab heterozygotes are asymptomatic, and homozygous individuals have hemolytic anemia with febrile illnesses. Coinheritance of Hb S and Hb O Arab produces clinically severe disease, with hemolytic anemia, jaundice, vaso-occlusive complications (pain crises and stroke), pneumonia, acute chest syndrome, and sepsis (4,6 ). Sickle and target cells, polychromasia, and sometimes Howell-Jolly bodies are detected on peripheral blood smears.…”

“…Like Hb S/S, Hb S/O Arab has reduced oxygen affinity and a lower gelling point for concentrated deoxygenated Hbs (7,8 ). When deoxygenated, Hb S/O Arab induces irreversible sickling of red cells (6,7 ), which are hemolyzed or cleared through the reticuloendothelial system. Sickled cells block the narrow capillaries, causing membrane damage and vaso-occlusive events ( 4).…”

“…Dehydrated red cells of S/C disease are typically microcytic (2 ), whereas patients with S/O Arab disease are often normocytic. As with our patient, microcytosis is seen in some patients with S/O Arab disease (6 ).…”

Bone marrow necrosis and sickle cell crisis associated with double heterozygosity for HbS and HbOARAB

“…Among the patients with HbOARAB mutation (b globin chains: 121 Glu?Lys), HbOARAB heterozygotes show no related clinical manifestations whereas homozygotes present a mild haemolysis with borderline splenomegaly. The double heterozygoty for HbS and HbOARAB (Hb S/O-Arab) is rare and results in a severe sickling hemoglobinopathy as homozygous sickle cell anemia [4]. The enhancing role of the HbO-Arab on the sickling effect of HbS is driven by electric charge modifications of the erythrocytes' membrane resulting in denser and more spherical erythrocytes, a dysfunction of K:Cl co-transport system leading to erythrocyte's dehydration and intracellular HbS polymerization enhancement and stabilization [5].…”