A diabetic patient in whom Hb Weesp was incidentally detected when her HbA1c level was measured.

The level of glycated hemoglobin A1c (HbA1c) is widely used to monitor long-term glycemic control in patients with diabetes mellitus. There are more than 30 methods for measuring HbA1c levels. In recent times, high-performance liquid chromatography (HPLC) has become the most commonly used method in Japan. However, HPLC-based HbA1c level measurements do not accurately reflect glycemic control in the presence of Hb variants. We report the case of a patient with type 2 diabetes mellitus, who was incidentally found to having an extremely rare Hb variant. A 69-year-old Japanese female visited our clinic and was diagnosed with diabetes mellitus. Her HbA1c level, which was measured using HPLC at our clinic, could not be determined. DNA sequencing revealed a heterozygous mutation in the α1 globin gene (HBA1: c.301C > T, p.Leu101Phe). Hb Weesp was detected. Many Hb variants have been reported; however, to the best of our knowledge, this is only the second report about Hb Weesp in the world and the first from Japan. Clinicians should consider the possibility of Hb variants in cases in which abnormal elution patterns are detected during the measurement of HbA1c using HPLC.