High-oxygen-affinity hemoglobinopathy-associated erythrocytosis: Clinical outcomes and impact of therapy in 41 cases.

We describe presenting features, treatment strategies, and follow-up events involving 41 patients (median age 39 years, range 1-81; 54% males) with high oxygen affinity (HOA) hemoglobinopathy-associated erythrocytosis, seen at our institution (1973-2020). Thirty-four (83%) patients carried β-chain (13 Malmo, 4 Olympia, 3 San Diego, 2 Wood) and 7 (17%) α-chain (4 Dallas and one each Columbia-Missouri, Jackson, and Wayne) variants. Median (range) hemoglobin (Hgb)/hematocrit (Hct), serum erythropoietin and p50 were 18 g/dL/52.9% (16-21.9/48-66), 10.4 mIU (4-36.3), and 20 mmHg (12-25), respectively. Family history was documented in 24 patients and history of thrombosis in two (5%). Treatment included phlebotomy in 23 and antiplatelet therapy in 21 patients. At a median follow-up of 10 years, 23 (56%) patients reported one or more symptoms that were thought to be related to their increased Hct while thrombosis was documented in 10 (24%) patients. Neither Hgb/Hct level nor active phlebotomy showed a significant correlation with either thrombotic or nonthrombotic symptoms (p > .1 in all instances). Among 23 pregnancies recorded, 78% resulted in live births and no fetal loss was attributed to erythrocytosis. The current study does not implicate Hgb/Hct level as a major contributor of morbidity in HOA hemoglobinopathy-associated erythrocytosis and suggests limited therapeutic value for phlebotomy.