A patient with a hemoglobin variant (Hb JLome) unexpectedly detected by HPLC for glycated hemoglobin (Hb A1c)

A rare hemoglobin variant, Hb JLome, was identified by chance in a male patient with diabetes mellitus (DM). The patient had no evidence of anemia or hemolysis. However, when his glycated hemoglobin (Hb A1c) was examined by high-performance liquid chromatography (HPLC) to assess the state of his DM, an abnormal Hb was unexpectedly detected on the chromatogram. The morphology of the red blood cells was normal. A fast-moving band as well as a normally moving Hb band, of roughly equal intensities, were observed by cellulose acetate membrane electrophoresis. The oxygen equilibrium curve was essentially normal (P50 = 3.59 kPa). In other words, the ability of the patient's Hb to carry oxygen was nearly the same as that of typical Hb A. The stability of his Hb in isopropanol was normal, and all the functions of his Hb that were tested were essentially normal. The identity of the abnormal Hb was finally determined, by sequencing the globin gene, to be Hb JLome, which is produced by a point mutation changing AAG to AAC at the 59th codon in exon 2 of the Hb beta chain. As previously reported, replacing the beta 59 lysine with asparagine does not affect the function of Hb or the red blood cells. There have been only five documented cases of Hb JLome in Japan. Interestingly, all these cases are from Kyushu Island. When an abnormal chromatogram for Hb A1c is unexpectedly obtained, it is worthwhile searching for an abnormal Hb, even if there are no signs that suggest its existence, such as anemia, hemolysis, erythrocytosis, or cyanosis.