First Observation of Hemoglobin Ypsilanti in Saudi Arabia: A High Oxygen Affinity Hemoglobin Presenting with Extreme Erythrocytosis

Abstract

Abstract High oxygen affinity hemoglobin (HOAH) variants are rare hemoglobinopathies sometimes associated with congenital erythrocytosis. Patients with HOAH are usually asymptomatic and are incidentally discovered when unexplained erythrocytosis is observed in the complete blood count. Here, we report the first patient with hemoglobin (Hb) Ypsilanti from high-altitude Southern Saudi Arabia, who presented with chronic extreme erythrocytosis (polycythemia) with an Hb concentration of 23 g/dL and hematocrit of 70%. The patient lacked any finding suggestive of secondary erythrocytosis, and the evaluation for acquired polycythemia vera was negative. Hb protein analysis and genetic testing confirmed the presence of a high-affinity Hb variant. Living at high altitude contributed to the presentation of extreme erythrocytosis. Besides highlighting important clinical and diagnostic characteristics, this case illustrates two important diagnostics caveats: high-affinity Hb can be misdiagnosed as another more common qualitative hemoglobinopathy such as Hb S or Hb D carrier state, and it can interfere with HbA1C analysis.