Despite no CD4 gene defect having been previously reported in humans, several case reports have previously described the association of persistent idiopathic CD4+ T-cell lymphopenia, in the absence of infection with HIV 1 or HTLV-1/2, and/or of a well-defined (primary or secondary) immunodeficiency disease, with recalcitrant warts and generalized verrucosis (58–64). Here, CD4 is linked to immunodeficiency disease.