A diagnosis of herpes zoster can be made at the bedside by a Tzanck smear preparation of scrapings from the floor of the vesicles, which will reveal multinucleated giant cells on direct microscopy, or by direct fluorescent antibody tests, presence of high or rising titers to VZV, or by culture studies.[4] It is imperative that herpes zoster be differentiated from zosteriform herpes simplex, which is more common in children, by direct fluorescent monoclonal antibody test or by detection of serum specific IgM by the indirect fluorescent antibody method. The gene discussed is CD40LG; the disease is herpes zoster.