Counts and areas of S-100-positive epidermal dendritic cells in atypical molluscum contagiosum affecting HIV+ patients

Molluscum contagiosum is a common and self-limiting viral infection, that in HIV+ patients courses as an opportunist affection with atypical clinical features. Impaired cell-mediated immune response could be involved in such atypical growth. We evaluated the density and area of Langerhans cells (LC) using S-100 immunohistochemistry in seven atypical molluscum contagiosum. LC density was quantified by three different methods using computer-assisted morphometry as well as estimating the relative area of LC with respect to epidermal area. Results were compared with two control groups (normal skin specimens and molluscum contagiosum affecting non-AIDS healthy patients). We found a virtual absence of LC in areas of molluscum lesions affecting both HIV+ and non-AIDS patients. Likewise we observed an evident decrease in LC density in perilesional epidermis of atypical molluscum with respect to both control groups. Upon comparing the counts and areas, we observed that this reduction in LC count was statistically significant only when considering LC related to length of basement membrane in atypical molluscum with respect to normal skin specimens. Our finding of a reduced number of LC in the perilesional epidermis of HIV+ patients with atypical molluscum could explain the high frequency and clinical challenge of molluscum contagiosum in immunocompromised people. In spite of these results, further studies of LC kinetics and functions are required to precisely elucidate their role in the course of molluscum contagiosum in HIV+ patients.