Punctate porokeratotic keratoderma: some pathogenetic analyses of hyperproliferation and parakeratosis

An 82-year-old Japanese woman had numerous palmoplantar keratotic plugs and pits, resembling 'music box spines'. Histological examination revealed compact columns of parakeratosis in the horny layer. Ultrastructually, the affected stratum corneum contained numberous variable-sized pyknotic nuclei, and cells in the stratum granulosum contained fewer keratohyalin granules. Autoradiographic analysis by [3H]thymidine [3H]TdR incorporation into epidermal cells of affected skin slices in organ culture revealed that only basal cells below the keratotic plug were stimulated to proliferate. Two-dimensional gel electrophoresis revealed that palmar keratotic plugs contained the keratin filaments that are specifically present in the plantar viable epidermal layer, or other hyperproliferative epithelial cells.