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.