Hb Buffalo [α89(FG1)His→Gln (α1)], Observed Solely and in the Presence of an Hb S [β6(A3)Glu→Val] Heterozygosity

Abstract

The hemoglobin (Hb) pattern of a 32-year-old Somali male living in The Netherlands, during routine diabetes mellitus monitoring, showed two more peaks in addition to the characteristic heterozygous Hb A/S pattern. A major peak of 15% faster than Hb A, and a minor one of 10.8%, overlapping Hb A2 and the glycated Hb S1c fraction were present. The patient was not anemic or microcytic but had a low haptoglobin level, possibly indicating a slightly elevated red blood cell (RBC) turnover. Hb S was confirmed by a sickle test and at the DNA level. The DNA sequence of the alpha1 gene revealed a C-->G transversion at position 89, changing the local positively charged histidine to a neutral glutamine. This mutant has been previously described in a Yemenite woman and two apparently unrelated Somali males. Our case is the first showing Hb Buffalo in combination with Hb S and a G6PD deficiency, and is again observed in a Somali. No functional abnormalities associated with mutations at this amino acid residue are reported in the literature. Also, in this case no sign of any hematological abnormalities that could not be explained by the Hb S heterozygosity G6PD deficiency was found. The abnormal alpha chain is expressed at the expected rate and without thalassemic effect or instability. The mutated alpha chain seems to associate with a slight preference to the beta(A) (15%) rather than with the beta(S) counterpart. The sum of both Hb A(Buffalo) and Hb S(Buffalo) results in about 19-20% of total Hb. This figure is in agreement with a stable mutant of the alpha1 gene.

Hb Olivet (HBA1: C.40G > A; p.Ala14Thr), a Novel Silent Hemoglobin Variant in Two Families of Distinct Origin

“…However, in our experience about 10.0-15.0% of the cases sent to our reference laboratory by conscientious doctors to exclude or confirm a-thal in the absence of iron deficiency, is not caused by deletions but by known or unknown point mutations. One should be aware of the fact that these defects, although mild or asymptomatic in the carrier, may cause Hb H (b4) disease if associated with a 0 -thal defects (1)(2)(3)(4)(5). We present here a short article in which two families of different ethnicity and carrying a new variant, are described with the full characterization of the defect and with some additional details on expression and possible thalassemic effect.…”