Internal medicine
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A 74-year-old male patient with diabetes mellitus and hypertension who had been treated for a long period was admitted to our hospital. Laboratory data on admission revealed high values for fasting blood sugar and fructosamine, 219 mg/dl and 389 mumol/l respectively, while the concentration of glycated hemoglobin (HbA1c) was low (3.0%). ⋯ The structural analysis indicated that this abnormal Hb was Hb Riyadh [beta 120 (GH3) Lys-->Asn]. The low value of HbA1c despite the high blood glucose level may be attributed to this abnormal hemoglobin.