A Case of Variant Hemoglobin, Hb Prato [α₂ 31 (B12) AGG (Arg) →AGT (Ser) ], Found at a Periodic Health Checkup

Abstract

A 28-year-old man was referred to our hospital on suspicion of diabetes. While his HbA1c was 8.6 % as measured by high-performance liquid chromatography (HPLC G8), his fasting blood glucose was 89 mg/dL, and glycated albumin was 12.3 %, indicating a discrepancy between his HbA1c value and fasting blood glucose and glycated albumin values. His HPLC-HbA1c fraction (SA1c) was wide, with the shoulder located between the A0 peak and SA1C peak. Ultra-fast liquid chromatography revealed an abnormal peak, except for the A1c and A0 peaks. Therefore, his Hb was supposed to be a variant Hb. A gene analysis revealed a heterozygous mutation of the α2globin chain [α2 31 (B12) AGG (Arg) →AGT (Ser)], and he was diagnosed with Hb Prato, showing large and small red cells, an increased reticulocyte count, an mild instability to isopropanol. To our knowledge, this is the second reported case of Hb Prato in Japan. According to Globin Gene Saver, the percentage variant of Hb Prato is 20 %-30 % of total Hb tetramers. The percentage variant in our case was suspected to be 3.5 %. The first Japanese case showed a percentage variant of around 4 %, as calculated from their reports. There may have been some difference with regard to X between these Japanese cases and previously reported Italian cases.