Microscopic sections revealed papillomatosis and compact orthokeratotic hyperkeratosis. The granular layer was markedly thickened, with vacuolated keratinocytes exhibiting perinuclear edema and numerous binucleate cells. No significant epidermolysis or acantholysis was seen. Other family members had had similar clinical presentations and had previously been studied, although this information was not known at the time that the patient described herein was initially seen. Electron microscopy of skin specimens from those relatives revealed abnormal organization of keratin intermediate filaments with cytoplasmic shell formation.1