We report a third family affected with ichthyosis bullosa of Siemens, and we further delineate the clinical spectrum of this mild type of epidermolytic hyperkeratosis. Erythroderma had never been present in any of the affected individuals. All of them exhibited a brownish, rimpled hyperkeratosis, the main characteristic sites being the joints, the shins and the periumbilical region. Blistering occurred after slight mechanical trauma and even after sweating, resulting in superficially denuded areas. Two affected family members also suffered from chronic, relapsing pustular eruptions surrounded by a transient erythematous flare. Light- and electron-microscopic examination revealed epidermolytic hyperkeratosis limited to the upper part of the epidermis. The pustular lesions were found to be subcorneal blisters filled with neutrophils. Ichthyosis bullosa of Siemens can be clearly distinguished from bullous ichthyosiform erythroderma. The observation of subcorneal pustular dermatosis occurring in this phenotype provides further evidence for the genetic heterogeneity of epidermolytic hyperkeratosis.