Ichthyosis

Ichthyosis (plural ichthyoses) is a heterogeneous family of at least 28, generalized, mostly genetic skin disorders. All types of ichthyosis have dry, thickened, scaly or flaky skin. In many types there is cracked skin, which is said to resemble the scales on a fish; the word ichthyosis comes from the Ancient Greek ιχθύς (ichthys), meaning "fish." The severity of symptoms can vary enormously, from the mildest types such as ichthyosis vulgaris which may be mistaken for normal dry skin up to life-threatening conditions such as harlequin type ichthyosis. The most common type of ichthyosis is ichthyosis vulgaris, accounting for more than 95% of cases.

Types
There are many types of Ichthyosis and an exact diagnosis may be difficult. Types of Ichthyosis are classified by their appearance and their genetic cause. Ichthyosis caused by the same gene can vary considerably in severity and symptoms. Some Ichthyoses don't appear to fit exactly into any one type. Also different genes can produce Ichthyoses with similar symptoms. The most common or well-known types are as follows:

Genetic ichthyoses

 * Ichthyosis vulgaris
 * X-linked ichthyosis
 * Congenital ichthyosiform erythroderma (nbCIE)
 * Epidermolytic hyperkeratosis (bullous ichthyosis, bCIE)
 * Harlequin type ichthyosis
 * Ichthyosis bullosa of Siemens
 * Ichthyosis hystrix
 * Ichthyosis lamellaris (lamellar ichthyosis)

Ichthyoses with additional characteristics

 * Carvajal syndrome
 * CHILD Syndrome
 * Conradi-Hünermann syndrome
 * Darier's disease
 * Erythrokeratodermia variabilis (Erythrokeratodermia figurata variabilis, Mendes da Costa type erythrokeratodermia)
 * IFAP syndrome (Ichthyosis follicularis)
 * Keratitis-ichthyosis-deafness syndrome
 * Netherton syndrome
 * Neutral lipid storage disease (Dorfman-Chanarin syndrome)
 * Refsum's disease
 * Rud syndrome
 * Senter syndrome
 * Sjögren-Larsson syndrome
 * Tay syndrome (IBIDS syndrome, Trichothiodystrophy)

Non-genetic ichthyosis

 * Ichthyosis acquisita

Diagnosis
A physician often can diagnose ichthyosis by looking at the skin. A family history is very useful. In some cases, a skin biopsy is done to help to confirm the diagnosis. In a biopsy, a small piece of skin is removed and examined under a microscope. In some instances, genetic testing may be helpful in making a diagnosis. Diabetes has not been linked to acquired ichthyosis or ichthyosis vulgaris.

Ichthyosis is not more or less common in any ethnic group. As of now, there is no way to prevent ichthyosis since it is often of a genetic nature.

Treatments
Treatments for ichthyosis often take the form of topical application of creams and emollient oils, in an attempt to hydrate the skin. Retinoids are also used for some conditions. Exposure to sunlight may improve or worsen the condition.

There can be ocular manifestations of ichthyosis, such as corneal and ocular surface diseases. Vascularizing keratitis, which is more commonly found in congenital keratitis-ichythosis-deafness (KID), may worsen with isotretinoin therapy.

Ichthyosis in animals
Ichthyosis or ichthyosis-like diseases exist for several types of animals, including cattle, chickens, llamas, mice, and dogs. Ichthyosis of varying severity is well documented in some popular breeds of domestic dogs. The most common breeds to have ichthyosis are Golden retrievers, American bulldogs, Jack Russell terriers, and Cairn terriers.