Hb St. Jozef, a val→leu N-terminal mutation leading to retention of the methionine, and partial acetylation found in the globin gene in cis with a -α3.7 thalassemia deletion

We report a new hemoglobin (Hb) variant found in a 6-year-old girl of Moroccan origin, living in the Dutch city of Gouda. The child was referred because of microcytic and hypochromic parameters. A normal zinc protoporphyirin (ZPP) value excluded iron deficiency and gap-polymerase chain reaction (gap-PCR) revealed a heterozygosity for the common -alpha(3.7) thalassemia deletion, partially justifying the hematological picture. The Hb pattern on alkaline electrophoresis and capillaiy electrophoresis was normal, while a fraction of 9% preceding the Hb A peak, remained visible on different high performance liquid chromatography (HPLC) devices. This fraction, located in front of the Hb A peak, is usually considered as a Hb A derivate that becomes more expressed in older samples. However, the sample, was freshly collected and the peak unusually evident. Therefore, direct sequencing of the a-globin genes was performed revealing a GTG -> CTG transversion at codon of the alpha 1-globin gene or of the hybrid gene. This point mutation induces a single amino acid substitution from valine to leucine. Electrosproy-mass spectrometry (ES-MS) analysis revealed, in addition to this substitution, that the N-terminal methionine was retained and that about 20% of the valiant was acetylated. As expected for an association with alpha -alpha(3.7)-thalassemia (that) deletion, the non acetylated and acetylated abnormal a chain amounted to 32% of the total alpha chains. Family studies revealed that the mutated codon was located in cis of the deletion.