Frequency of -Globin Gene Triplications and Their Interaction with -Thalassemia Mutations

Our protocol for specialized diagnostics includes routine -globin gene analysis for all blood samples referred to our diagnostic laboratory. -Globin gene triplication is found to be present in more than 1% of samples tested. Since all cases with single -gene triplications are associated with normal hematological parameters, we assume that preselection does not bias our observation and that -globin gene triplications should be expected at the same frequency in the unselected Dutch multiethnic population as well. We have compared the average hematological parameters of -thalassemia (-thal) carriers with those of carriers with an associated -gene triplication. In all cases, a single additional gene had a very limited effect on the -thal minor phenotypes.