Melkersson Rosenthal syndrome: a histopathologic mystery and dermatologic challenge.

Melkersson Rosenthal syndrome (MRS) is rare disease of unknown etiology characterized by orofacial edema, facial nerve palsy and fissured tongue. Microscopically, it shows epithelioid non-caseous granulomas; however, edema and perivascular lymphocytic infiltrates have been described. Two different clinical forms of MRS are presented in this report. In the complete form (Case 1), the main histopathologic finding was a non-necrotizing granulomatous inflammation with 56% of the total number of cells composed of B cells (CD 20(+) ) principally located in the granuloma's center and 33% being T cells predominating in the surrounding area, of which 48% were CD 4(+) and 16% were CD 8(+) lymphocytes. In the monosymptomatic form (Case 2), the inflammatory cells were dispersed into the connective tissue without granulomatous formation. B cells were scanty, and 78% of the cells were CD 45(+) T cells, with 46% and 34%, CD 8(+) and CD 4(+) phenotype, respectively. These cases showed different clinical, histopathological and immunohistochemical forms of MRS, suggesting different host immune responses.