Ichthyosis bullosa of Siemens: a unique type of epidermolytic hyperkeratosis.

We report the second family of ichthyosis bullosa, an entity that was first described by Siemens in 1937 and since then has fallen into oblivion. Clinically, ichthyosis bullosa is characterized by blistering resembling epidermolysis bullosa simplex and by generalized, yet circumscribed dark gray hyperkeratoses covering mainly the arms and the legs. Lichenification and superficially denuded areas (mauserung) are further prominent features. Histology disclosed intracorneal blister formation corresponding to the mauserung phenomenon and epidermolytic hyperkeratosis that was confined to the granular layer and to the uppermost layers of the prickle cells. On electron microscopic examination the keratinocytes of these layers displayed structural alterations of tonofilaments as usually observed in epidermolytic hyperkeratosis. Thus ichthyosis bullosa shares with bullous ichthyosiform erythroderma blistering and epidermolytic hyperkeratosis, but can be distinguished from this wellknown disease by the lack of erythroderma, by the mauserung phenomenon, by the confinement of acanthokeratolysis to the superficial layers of the epidermis, and by intracorneal blistering.