[Hb Hirosaki hemoglobinopathy initially suspected due to low oxygen saturation levels and abnormally low HbA1c levels].

More than 1,200 hemoglobin variants are identified worldwide, and approximately 200 variants are detected in one of 3,000 Japanese people. Most of these patients are asymptomatic; however, some patients had hemolytic anemia or cyanosis. Herein, we report a case of a 49-year-old woman with prolonged fatigability after experiencing symptoms of common cold and intermittent brown urine. Her clinical data showed mild hemolysis, a disparity between SpO2 (93%) and pO2 (85.2 mmHg), and abnormally low HbA1c levels (3.7%). These findings lead to the diagnosis of unstable hemoglobin variant, Hb Hirosaki. A simple series of tests using pulse oximetry, an arterial blood gas analysis, measurement of HbA1c levels, or identifying the HPLC chromatogram of HbA1c can be the factors associated with the diagnosis of hemoglobinopathy.