Disseminated bilateral hyperkeratotic variant of porokeratosis Mibelli.

Clinical, histopathological, and ultrastructural features of a new clinical variant of porokeratosis Mibelli (PM) are presented. We report a solitary case of a patient, male aged 62, who developed disseminated verrucous nodules on the buttocks and the lower extremities 3 years before diagnosis. Histopathologically, all specific signs of the keratinization disorder of PM were demonstrable; in addition, however, multiple cornoid lamellae were found at the margin as well as in the center of the lesions, which only in part showed relationships to the epidermal appendages. In the papillary dermis, numerous ectatic capillaries were conspicuous. Using electron microscopy the same specific abnormalities of the keratinization process as known from classical cases of PM could be demonstrated: autophagocytic cells that revealed perinuclear edematization and vacuolization, accumulation of autophagic vacuoles and heterolysosomes, and dyskeratotic corps ronds-like cells that become transformed to fibrillar or Civatte bodies. Problems of the classification, differential diagnosis, and pathomorphogenesis are discussed.