Composite keratohyaline granules in palmoplantar keratoderma: an ultrastructural study

We report the results of an ultrastructural study of the hyperkeratotic epidermis in 23 cases of palmoplantar keratoderma (PPK) comprising 8 inherited keratoderma, 8 keratoderma climactericum in menopausal women and 7 symptomic keratoderma. In all but one of the cases of inherited PPK and keratoderma climactericum, composite keratohyalin (KH) granules were found in granular cells of the interductal epidermis, which were similar to those found in the rat and in some other conditions. In the cases of symptomatic keratoderma, e.g. secondary to eczema, the appearance of the KH granules did not differ from that of granules observed in two normal plantar skin samples. While the real role played by these granules is unknown, they could constitute a differentiation marker of intraepidermal duct cells, and their abundance in PPK suggest that intraepidermal sweat ducts may play a part in PPK histogenesis.