ICHTHYOSIS, or XERODERMA  , a general thickening of the whole skin and marked accumulation of the epidermic elements, with atrophy of the sebaceous glands, giving rise to a hard, dry, scaly condition, whence the names, from Ixebs, fish, and epos, dry, 3442a, skin . This disease generally first appears in infancy, and is probably congenital . It differs in intensity and in distribution, and is generally little amenable to any but palliative remedies, such as the regular application of oily substances . Ichthyosis lingualis (" smokers' tongue "), a variety common in heavy smokers, occurs in opaque white patches on the tongue, gums and roof of the mouth . Cancer occasionally starts from the patches . The affection is obstinate, but may disappear spontaneously .