Hb Grove City [β38(C4)Thr→Ser, ACC>AGC; HBB: c.116C>G]: A New Low Oxygen Affinity β Chain Variant

Abstract

A previously unreported β chain hemoglobin (Hb) variant, Hb Grove City [β38(C4)Thr→Ser, ACC>AGC; HBB: c.116C>G], was discovered in a woman who presented with hypoxia and mild anemia. Her young daughter also tested positive for the variant and displayed similar symptoms. Hemoglobin-oxygen dissociation testing confirmed right-shifted oxygen dissociation curves. A corresponding Hb variant was detected by high performance liquid chromatography (HPLC) and intact mass spectrometry (MS) but was not detected by capillary electrophoresis (CE), isoelectrofocusing (IEF) or alkaline or acid electrophoresis. DNA sequencing analysis confirmed a β-globin gene mutation. All three previous mutations at this locus affect oxygen affinity, as does this new variant. This newly described variant showed variable stability results and therefore may be mildly unstable but is not associated with microcytosis, significant hemolysis or clinically evident cyanosis. It is important to consider hemoglobinopathies in patients who are anemic and have unexplained hypoxia. Arterial blood gas and p50 evaluations may prevent unnecessary diagnostic interventions. Additionally, Hb variants with altered oxygen affinity can be electrophoretically silent; therefore, multiple methods including MS and/or DNA sequencing are warranted when clinical suspicion is high.