Diagnosis of hemogobinopathies in the clinical laboratory: an occult Hofu hemoglobin on HPLC

Abstract

Objectives: Hemoglobinopathies are disorders affecting the structure, function and/or production of hemoglobin. These conditions are caused by mutations in the genes encoding globin synthesis. The highly variable clinical manifestations of hemoglobin disorders range from asymptomatic forms to severe anemia. Laboratory tests are crucial for diagnosis.

Case presentation: We report the case of a patient who presented with asthenia. Since the patient had a family history of hemoglobonipathies, screening for erythropathies was performed. High-resolution liquid chromatography (HPLC) showed a normal distribution of hemoglobin levels. In contrast, capillary zone electrophoresis at alkaline pH demonstrated an unidentified rapid migration peak. Genetic testing revealed a mutation in the HBB gene causing Hofu hemoglobin disease.

Conclusions: The hemoglobin variant Hofu is slightly unstable. While heterozygous carriers most frequently remain asymptomatic, they may develop anemia in the presence of other concomitant disorders. Distinctively, the retention time of Hb Hofu on HPLC is very close to that of HbA (0) and they often elute together. Therefore, Hb Hofu may remain masked, thereby leading to the misinterpretation of test results.

Keywords: hemoglobin Hofu; hemoglobinopaty; red blood cell series.

Figure 1:

HPLC chromatography (BIO-RAD, D-10) coupled with photometric detection. Results are expressed in percentages and retention times: HbA: 82.3 %. 1.73 min; HbA₂: 3.4 %. 3.36 min; HbF: 1.4 %. 0.46 min; HbAc: 5.1 %. 0.84 min.

Figure 2:

Capillary electrophoresis graph (Capillarys 2, Sebia) demonstrating peaks. From left to right, the grey peak indicates an unidentified peak, 31.9 %. The pink peak on the right represents HbA, 64.2 %. Next to the HbA peak, there is a small orange peak that represents HbF. On the right side, there is a yellow peak where HbA₂ migrates, 3.4 %.