HbF in the adult: could its composition discriminate normal from abnormal foetal globin gene expression?

The relative proportions of the two gamma chain species ((G)gamma and (A)ga mma) have been reinvestigated in newborns, during the physiological switch from foetal to adult haemoglobin, and in adults with some persistent expres sion of HbF. In newborns, with about 80 % HbF, the (G)gamma percentage was close to 70 % while in adult RBC, with less than 0.5 % HbF, the (G)gamma ch ain was almost non-detectable and may reflect the completion of the foetal to adult switch. Conversely, in adult patients with HbF above 0.6 %, usuall y accompanying some degree of marrow stimulation, the relative ratio of (G) gamma varied between 40 and 60 %, independently of HbF level. This ratio co rresponds to what has been described in the literature as being the adult t ype of HbF. In all the cases where we found higher levels of (G)gamma, the results could be explained by the presence of a specific genetic background such as the Senegalese haplotype in sickle cell disease. (C) 2000 Academie des sciences/ Editions scientifiques et medicales Elsevier SAS.