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

Abstract

Hemoglobin S/OArab (Hb S/OArab) is a rare compound heterozygous hemoglobinopathy characterized by the presence of two variant β-globin chains: β6Glu → Val (Hb S) and β121Glu → Lys (Hb OArab). The diagnosis of Hb S/OArab requires electrophoresis on both cellulose acetate and citrate agar, since Hb OArab co-migrates with Hb C at alkaline pH and close to Hb S at acidic pH. To date only case reports and small series of patients with Hb S/OArab have been described. To better characterize the clinical and laboratory aspects of this unusual disorder, we reviewed the Duke University Medical Center experience. We identified 13 African-American children and adults with Hb S/OArab ranging in age from 2.7 to 62.5 years. All patients had hemolytic anemia with a median Hb of 8.7 gm/dL (range 6.1–9.9 gm/dL), and a median reticulocyte count of 5.8% (range 1.2–10.3%). The peripheral blood smear typically showed sickled erythrocytes, target cells, polychromasia, and nucleated red blood cells. All 13 patients have had significant clinical sickling events including acute chest syndrome (11), recurrent vasoocclusive painful events (10), dactylitis (7), gallstones (5), nephropathy (4), aplastic crises (2), avascular necrosis (2), leg ulcers (2), cerebrovascular accident (CVA) (1), osteomyelitis (1), and retinopathy (1). Four patients have died, including two from pneumococcal sepsis/meningitis at ages 5 and 10 years, one of acute chest syndrome at age 14 years, and one of multiorgan failure at age 35 years. We conclude that Hb S/OArab disease is a severe sickling hemoglobinopathy with laboratory and clinical manifestations similar to those of homozygous sickle cell anemia. Am. J. Hematol. 60:279–284, 1999. © 1999 Wiley-Liss, Inc.