Autoantibodies to melanocytes and characterization of melanophages in patients affected by a new variant of endemic pemphigus foliaceus.

BACKGROUND: Melanin and melanophages are commonly seen under the basement membrane zone of the skin in patients affected by a new variant of endemic pemphigus foliaceus in El Bagre, Colombia (El Bagre-EPF). OBJECTIVE: Our study was conducted to determine the nature of these pigmentary alterations. METHODS: We utilized clinical, histopathologic and immunologic techniques including direct and indirect immunofluorescence, immunohistochemistry, Bielschowsky staining and immunoelectron microscopy studies. RESULTS: In the El Bagre-EPF patients, we detected dermal melanin in melanophages and antigen-presenting cells, in close proximity to neural and vascular markers. The melanophages consisted of a mixed population expressing CD68, myeloid/histoid antigen and S-100 protein. By immunoelectron microscopy, the presence of autoantibodies in proximity to melanin granules was confirmed within the melanocytes utilizing 10-nm gold particles. CONCLUSION: Dermal antigen-presenting cells, including melanophages, seem to contain a diverse combination of molecules, representative of an immunologic process where these cells are engulfing both autoantigens and/or cellular debris in El Bagre-EPF. Autoantibodies to discrete components of melanocytes were also identified; the clinical and immunologic significance of these findings remains unknown. Our work may provide a possible explanation of a darkened complexion in patients affected by endemic pemphigus foliaceus.