**3.1.2 Infectious ablation of the thymus**

Human immunodeficiency virus (HIV)-infected children usually show faster AIDS progression than their adult counterparts. Newborns infected during fetal development (intra-uterine infection versus infection in the birth canal) show important immune alterations from the first day of life. Due to lack of thymic function measurements, thymus ablation was defined thru peripheral observations as T lymphopenia involving both CD4 and CD8 T cell subsets. More severe thymic deficiency was associated with worse clinical prognosis. Some of these vertically-infected children present an immunophenotypic profile even comparable with DiGeorge syndrome. Infectious thymus ablation is strongly correlated with earlier and faster AIDS progression (Kourtis et al., 1996) and increased mortality rates (Nahmias et al., 1998) when compared with children with preserved thymic function (usually infected at the birth canal).
