- Dry, rectangular scales on the skin. Like fish scales. From the Greek "ichthys" meaning fish. Ichthyosis is not one but rather a group of skin disorders characterized by noninflammatory scaling of the skin. Many different metaphors have been used to describe the appearance and texture of the skin in the various types and stages of ichthyosis, for example alligator skin, crocodile skin, collodion skin, porcupine skin and, of course, fish skin. Most ichthyoses are genetic (inherited). Some ichthyoses develop in association with various systemic diseases or be a prominent feature in certain genetic syndromes. The term "ichthyosis" is commonly used alone to refer to ichthyosis vulgaris. Ichthyosis vulgaris, also known as ichthyosis simplex, is inherited as an autosomal (nonsex-linked) trait and is characterized by scaly (fishlike) areas of skin. The first scaly skin problems usually appear after 3 months of age. The palms and soles are often affected. Areas that tend to be spared include the axillae (the armpits), the antecubital fossa (the inside area at the bend of the elbow) and the popliteal fossa (behind the knee). The gene responsible for ichthyosis vulgaris has been mapped to chromosome band 1q21. The product of this gene is thought to be a substance called filaggrin (abbreviated FLG) which may act as the "keratin matrix protein" in cells of the stratum corneum, one of the layers of the skin.
* * *Congenital disorders of keratinization characterized by noninflammatory dryness and scaling of the skin, often associated with other defects and with abnormalities of lipid metabolism; distinguishable genetically, clinically, microscopically, and by epidermal cell kinetics. SYN: alligator skin, fish skin, sauriasis. [ichthyo- + G. -osis, condition]- acquired i. a thickening and scaling of the skin associated with some malignant diseases ( e.g., Hodgkin lymphoma), leprosy, and severe nutritional deficiencies.- i. congenita SYN: lamellar i..- i. corneae an ocular complication of a congenital abnormality of the skin with corneal keratinization, dryness, and scaling.- i. fetalis 1. SYN: harlequin fetus. 2. recessive condition in Holstein and Norwegian red poll cattle resembling harlequin fetus in humans.- i. follicularis a form of autosomal dominant type of i., with horny follicular plugging of the extensor surfaces of the extremities; onset in early childhood.- harlequin i. [MIM*242500] a fetal form of i. thought to be distinct from lamellar i., with plaques having a diamondlike shape resembling the suit of a harlequin clown; the keratinocytes contain increased amounts of tonofibrils, which are fibrillar structural proteins; autosomal recessive inheritance.- lamellar i. [MIM*242300] a dry form of congenital ichthyosiform erythroderma, characterized by ectropion and large, coarse scales over most of the body with thickened palms and soles; may be fatal with complications of sepsis, protein, and electrolyte loss in the first year of life; histology shows hyperkeratosis, a prominent granular layer in the epidermis, slight acanthosis, many mitotic figures, and normal or reduced epidemal cell turnover. Autosomal recessive inheritance, caused by mutation in the gene encoding keratinocyte transglutaminase (TGM1) on chromosome 14q. SEE ALSO: collodion baby, harlequin fetus. SYN: i. congenita.- i. linearis circumflexa congenital or infantile migratory polycyclic erythema and scaling that shows a peripheral double margin; persists throughout life and may be associated with trichorrhexis invaginata in Netherton syndrome [MIM*256500]; autosomal recessive inheritance.- i. scutulata i. marked by diamond-shaped or shield-shaped lesions.- i. vulgaris [MIM*146700] an autosomal dominant trait, with onset in childhood of scales on the trunk and extremities but not on the flexural areas, and associated with atopy and prominent palmar and plantar markings; histologically, there is hyperkeratosis, absence of a granular layer in the epidermis, and normal epidermal cell turnover. SYN: hyperkeratosis congenita, i. simplex.- X-linked i. [MIM*308100] a form of i., with onset at birth or in early infancy and affecting males; characterized by scaling predominantly on the scalp, neck and trunk and progressing centripetally; the palms and soles are spared; histologic manifestations are hyperkeratosis, a granular layer in the epidermis, and normal epidermal cell turnover. X-linked recessive inheritance, caused by mutation in the steroid sulfatase gene (STS) on Xp. SYN: steroid sulfatase deficiency.
* * *ich·thy·o·sis .ik-thē-'ō-səs n, pl -o·ses -.sēz any of several congenital diseases of hereditary origin characterized by rough, thick, and scaly skin called also fishskin disease
* * *n.a genetically determined skin disorder (see genodermatosis) in which there is abnormal scaling of the skin (the scaly condition of the skin is reflected in the name of this disorder, which is derived from the Greek word for fish). Ichthyosis may be caused by a variety of genetic defects in skin shedding; the pattern of scaling varies according to the underlying defect. The commonest form, ichthyosis vulgaris, is inherited as an autosomal dominant and occurs in 1 in 300 of the population. Lamellar ichthyosis is a very rare condition in which the skin, particularly on the palms and soles, is thickened and lizard-like. Treatment of ichthyosis is mainly by the regular use of emollients. See also xeroderma.
* * *ich·thy·o·sis (ik″the-oґsis) [ichthy- + -osis] 1. any in a group of cutaneous disorders characterized by increased or aberrant keratinization, resulting in noninflammatory scaling of the skin. Metaphors sometimes used to describe the appearance or texture of the skin in various types or stages of ichthyosis include alligator, collodion, crocodile, fish, and porcupine skin. Most ichthyoses are genetically determined, but a few types may be acquired, usually developing in association with systemic diseases or genetic syndromes. 2. i. vulgaris. ichthyotic adj
Medical dictionary. 2011.