A 57-year-old female patient has had generalized cutaneous lesions since birth. Clinically there are patch- and band-like areas of erythrokeratotic and pigmented skin in reticular arrangement. The most important histological findings are band-like parakeratosis, psoriasiform acanthosis, vacuolization of the keratinocytes in the upper layers of the epidermis with a high frequency of binuclear cells, and deposits of amyloid in the dermis. Ultrastructurally, the formation of perinuclear shells built from a three-dimensional network of fine filaments is the most peculiar finding. Binuclear cells are frequently found from the first suprabasal layers. Oedematization of the perinuclear cytoplasm within the shells finally leads to vacuolization of the uppermost granular cells. The horny layer is parakeratotic and contains debris of nuclei and lipid vacuoles. In the clinically normal appearing skin within the reticular network, keratinization occurs in a completely normal fashion. In spite of a good response to retinoid treatment, perinuclear shells and binuclear cells remain demonstrable in involved regions. The clinical, histological and ultrastructural peculiarities of this case suggest the diagnosis of a special type of congenital disturbances of keratinization, which can be clearly distinguished from the well-known ichthyosiform dermatoses and other inborn errors of keratinization.