Noninflammatory scaly disorders in which polygonal gray or brown scales tend to be elevated at their periphery, causing them to appear to be separated from contiguous scales, findings that are seen in three conditions, namely, ichthyosis vulgaris (and its look-alike, acquired ichthyosis), X-linked ichthyosis, and lamellar ichthyosis. Other conditions purported to be ichthyosis, among them nonbullous congenital ichthyosiform erythroderma, ichthyosis hystrix, and ichthyosis linearis circumflexa, do not fulfill the criteria just set forth.