Hemoglobin S/O-ARAB: Thirteen new cases and review of the literature

Hemoglobin S/O-Arab (Hb S/O-Arab) is a rare compound heterozygous hemoglobi nopathy characterized by the presence of two variant beta-globin chains: be ta(6)Glu --> Val (Hb S) and beta(121)Glu --> Lys (Hb O-Arab) The diagnosis of Hb S/O-Arab requires electrophoresis on both cellulose acetate and citra te agar, since Hb O-Arab 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 w ith Hb S/O-Arab have been described. To better characterize the clinical an d laboratory aspects of this unusual disorder, we reviewed the Duke Univers ity Medical Center experience. We identified 13 African-American children a nd adults with Hb S/O-Arab ranging in age from 2.7 to 62.5 years. All patie nts 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 periphera l blood smear typically showed sickled erythrocytes, target cells, polychro masia, and nucleated red blood cells. Ail 13 patients have had significant clinical sickling events including acute chest syndrome (11), recurrent vas oocclusive painful events (10), dactylitis (7), gallstones (5), nephropathy (4), aplastic crises (2), avascular necrosis (2), leg ulcers (2), cerebrov ascular accident (CVA) (1), osteomyelitis (1), and retinopathy (1). Four pa tients 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 mu ltiorgan failure at age 35 years. We conclude that Hb S/O-Arab disease is a severe sickling hemoglobinopathy with laboratory and clinical manifestatio ns similar to those of homozygous sickle cell anemia. (C) 1999 Wiley-Liss, Inc.