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A mild form of ichthyosis characterized by excessive dryness of the skin due to slight increase of the horny layer and diminished water content of the stratum corneum from decreased perspiration, wind, or low humidity; seen with aging, atopic dermatitis, vitamin A deficiency, etc. [xero- + G. derma, skin]

- x. pigmentosum [MIM*278700] an eruption of exposed skin occurring in childhood and characterized by photosensitivity with severe sunburn in infancy and the development of numerous pigmented spots resembling freckles, larger atrophic lesions eventually resulting in glossy white thinning of the skin surrounded by telangiectases, and multiple solar keratoses that undergo malignant change at an early age; results from several rare autosomal recessive complementation groups in which DNA repair processes are defective, so that they are more liable to chromosome breaks and cancerous change when exposed to ultraviolet light. Severe ophthalmic and neurologic abnormalities are also found. SEE ALSO: De Sanctis-Cacchione syndrome.

xe·ro·der·ma .zir-ə-'dər-mə n a disease of the skin characterized by dryness and roughness and a fine scaly desquamation

a mild form of the hereditary disorder ichthyosis, in which the skin develops slight dryness and forms branlike scales. It is common in the elderly. Xeroderma pigmentosum is a rare genetically determined disorder (see genodermatosis) in which there is an inherited defect in the mechanism that repairs damage to DNA brought about by ultraviolet radiation (see DNA repair); this leads to multiple skin cancers. Affected individuals must avoid any exposure to sunlight.