PGP 9.5 neuronal marker may differentiate immunohistochemically HIV-related from Mediterranean and immunosuppression-associated Kaposi's sarcoma.

Mediterranean Kaposi's sarcoma (MKS), HIV-related KS (HIV-KS) and immunosuppression-associated KS (IS-KS), caused by human herpes virus 8 (HHV-8), share similar histological features. The aim of this study was to investigate differences in epidermal nerve fibers (ENFs) between the three KS types and controls. Skin biopsies from 23 HIV-KS, 16 MKS, 28 IS-KS patients and 18 controls, age-gender matched, were immunostained with PGP 9.5; ENFs in upper epidermal layer (EL) and penetrating the basement membrane were measured. The mean number of nerve fibers penetrating ENFs was significantly lower in HIV-KS (p < 0.001) compared to all other groups. MKS and IS-KS had comparable ENFs but lower than controls (p < 0.00 1). In the upper EL all groups had comparable ENFs and lower than controls. In conclusion, HIV-KS can be distinguished histologically from other types, by counting ENFs. Moreover, KS is associated with decreased ENFs, which may be a histological reflection of nerve damage. This is even more pronounced in HIV-KS patients and could be explained by a neurotoxic action of HHV-8, HIV, and their co-existence.