Definition of the Term “Ichthyosis”

Abstract

“Ichthyosis” is a descriptive term used for a variety of hereditary keratinization disorders [3]. These disorders are grouped together because they always are genetic in nature and share a conspicuous scaling which is generalized and affects the whole integument. Localized keratinization disorders which confine themselves to certain parts of the body, such as the group of palmoplantar keratoses or the group of erythrokeratoderma, are excluded [2]. Though not explicitly stated, the term “ichthyosis” conveys the picture of a static disease process which may show some seasonal variation but does not exhibit the spontaneous coming and going of skin lesions that is typical, for example, of Darier’s disease. Ichthyosis may be accompanied by erythroderma, and for historical reasons these types of ichthyosis are usually referred to as ichthyosiform erythroderma rather than ichthyotic erythroderma [1], though ichthyotic would be grammatically more logical [4]. I suggest that usage of the attribute “ichthyosiform” be restricted to nongenetic cornification disorders. Following this definition, ichthyosiform skin changes are always acquired (e.g., the ichthyosis-like condition in Hodgkin’s disease). The word “ichthyosis” is derived from the Greek word “ichthys”, which means fish. It was already used in the eighteenth century by Willan [5] and was coined at a time when characteristics of human diseases were compared to those occurring in the animal kingdom.