Ichthyosis

Ichthyosis is a family of genetic skin disorders characterized by dry, thickened, scaly skin.[1] The more than 20 types of ichthyosis range in severity of symptoms, outward appearance, underlying genetic cause and mode of inheritance (e.g., dominant, recessive, autosomal or X-linked).[2] Ichthyosis comes from the Greek ἰχθύς ichthys, literally "fish", since dry, scaly skin is the defining feature of all forms of ichthyosis.[3]

Ichthyosis
Other namesIchthyoses
Ichthyosis is characterized by generalised, scaly skin.
SpecialtyDermatology

The severity of symptoms can vary enormously, from the mildest, most common, types such as ichthyosis vulgaris, which may be mistaken for normal dry skin, up to life-threatening conditions such as harlequin-type ichthyosis. Ichthyosis vulgaris accounts for more than 95% of cases.[4]

Types

Many types of ichthyoses exist, and an exact diagnosis may be difficult. Types of ichthyoses are classified by their appearance, if they are syndromic or not, and by mode of inheritance.[5] For example, non-syndromic ichthyoses that are inherited recessively come under the umbrella term autosomal recessive congenital ichthyosis (ARCI).

Ichthyosis caused by mutations in the same gene can vary considerably in severity and symptoms. Some ichthyoses do not appear to fit exactly into any one type while mutations in different genes can produce ichthyoses with similar symptoms. Of note, X-linked ichthyosis is associated with Kallmann syndrome (close to the KAL1 gene). The most common or well-known types are:[5]

Non-syndromic ichthyosis
Name OMIM Mode Of Inheritance Gene(s)
Ichthyosis vulgaris 146700 Autosomal semi-dominant FLG
X-linked recessive ichthyosis 308100 X-linked recessive STS
Harlequin ichthyosis 242500 Autosomal recessive ABCA12
Congenital ichthyosiform erythoderma 242100 Autosomal recessive TGMI1, NIPAL4, ALOX12B, ALOXE3, ABCA12, CYP4F22, NIPAL4, LIPN, CERS3, PNPLA1, ST14, CASP14
Lamellar ichthyosis 242300 Autosomal recessive TGMI1, NIPAL4, ALOX12B, ALOXE3, ABCA12, CYP4F22, NIPAL4, LIPN, CERS3, PNPLA1, ST14, CASP14
Self improving congenital ichthyosis 242300 Autosomal recessive TGM1, ALOX12B, ALOXE3
Bathing suit ichthyosis 242300 Autosomal recessive TGMI1
Epidermolytic ichthyosis 113800 Autosomal dominant KRT1, KRT10
Superficial epidermolytic ichthyosis 146800 Autosomal dominant KRT2
Annular epidermolytic ichthyosis 607602 Autosomal dominant KRT1, KRT10
Ichthyosis Curth-Macklin 146590 Autosomal dominant KRT1
Autosomal recessive epidermolytic ichthyosis 113800 Autosomal recessive KRT10
Congenital reticular ichthyosiform erythroderma 609165 Autosomal dominant KRT1, KRT10
Epidermolytic nevi 113800 Postzygotic mosaicism KRT1, KRT10
Loricrin keratoderma 604117 Autosomal dominant LOR
Erythrokeratodermia variabilis 133200 Autosomal dominant GJB3, GJB4
Peeling skin disease 270300 Autosomal recessive CDSN
Keratosis linearis with ichthyosis congenita and sclerosing keratoderma 601952 Autosomal recessive POMP

Syndromic Ichthyosis
Name OMIM Mode Of Inheritance Gene (s)
X-linked recessive ichthyosis syndromic forms 308700 
300500
300533
 X-linked recessive STS
Ichthyosis follicularis with alopecia and photophobia syndrome 308205 X-linked recessive MBTPS2
Conradi-Hunermann-Happle syndrome 302960 X-linked dominant EBP
Netherton syndrome 256500 Autosomal recessive SPINK5
Ichthyosis-hypotrichosis syndrome 610765 Autosomal recessive ST14
Trichothiodystrophy 601675 Autosomal recessive ERCC2, ERCC3, GTF2H5
Trichothiodystrophy (non-congenital forms) 275550 
211390
601675
 Autosomal recessive C7Orf11, TTDN1
Sjögren-Larsson syndrome 270200 Autosomal recessive ALDH3A2
Refsum's disease 266500 Autosomal recessive PHYH, PEX7
Mental retardation, enteropathy, deafness, neuropathy, ichthyosis, keratoderma syndrome 609528 Autosomal recessive SNAP29
Arthrogryposis, renal dysfunction, cholestasis syndrome 208085 Autosomal recessive VPS33B
Keratitis-ichthosis-deafness syndrome 602450 
148210
 Autosomal dominant GJB2
Neutral lipid storage disease with ichthyosis 275630 Autosomal recessive ABHD5
Ichthyosis prematurity syndrome 608649 Autosomal recessive SLC27A4
Neu–Laxova syndrome 256520 
616038
 autosomal recessive PHGDH , PSAT1 and PSPH

Non-genetic ichthyosis

Diagnosis

A physician often can diagnose ichthyosis by looking at the skin. A family history is also useful in determining the mode of inheritance. In some cases, a skin biopsy is done to help to confirm the diagnosis while in others genetic testing may be helpful in making a diagnosis. Diabetes has not been definitively linked to acquired ichthyosis or ichthyosis vulgaris; however, there are case reports associating new onset ichthyosis with diabetes.[6]

Ichthyosis has been found to be more common in Native American, Asian, Mongolian groups. There is no way to prevent ichthyosis.

Ichthyosis is a genetically and phenotypically heterogeneous disease that can be isolated and restricted to the skin manifestations or associated with extracutaneous symptoms. One of which is limb reduction defect known as CHILD syndrome; a rare inborn error of metabolism of cholesterol biosynthesis that is usually restricted to one side of the body. One case with symptoms matching CHILD syndrome has been described as having a likely-different cause.[7]

Treatments

Treatments for ichthyosis often take the form of topical application of creams and emollient oils, in an attempt to hydrate the skin. Creams containing a high percentage of urea or lactic acid have been shown to work exceptionally well in some cases.[8] Application of propylene glycol is another treatment method. Retinoids are used for some conditions.

Exposure to sunlight may improve or worsen the condition. In some cases, excess dead skin sloughs off much better from wet tanned skin after bathing or a swim, although the dry skin might be preferable to the damaging effects of sun exposure.

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.

Other animals

Ichthyosis or ichthyosis-like disorders exist for several types of animals, including cattle, chickens, llamas, mice, and dogs.[9] 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.[10]

See also

References
  1. "Frequently Asked Questions". Foundation for Ichthyosis & Related Skin Types (FIRST). Retrieved 12 July 2017.
  2. thefreedictionary.com/ichthyosis citing: Gale Encyclopedia of Medicine. Copyright 2008
  3. "Ichthyosis". Health Information Library. Johns Hopkins Medicine. Archived from the original on 2 February 2009.
  4. Okulicz JF, Schwartz RA (2003). "Hereditary and acquired ichthyosis vulgaris". International Journal of Dermatology. 42 (2): 95–8. doi:10.1046/j.1365-4362.2003.01308.x. PMID 12708996. S2CID 20029085.
  5. Oji, Vinzenz; Preil, Marie-Luise; Kleinow, Barbara; Wehr, Geske; Fischer, Judith; Hennies, Hans Christian; Hausser, Ingrid; Breitkreutz, Dirk; Aufenvenne, Karin; Stieler, Karola; Tantcheva-Poór, Illiana (2017). "S1 guidelines for the diagnosis and treatment of ichthyoses - update" (PDF). JDDG: Journal der Deutschen Dermatologischen Gesellschaft. 15 (10): 1053–1065. doi:10.1111/ddg.13340. PMID 28976107. S2CID 27585177.
  6. Scheinfeld, N; Libkind, M; Freilich, S (2001). "New-onset ichthyosis and diabetes in a 14-year-old". Pediatric Dermatology. 18 (6): 501–3. doi:10.1046/j.1525-1470.2001.1862004.x. PMID 11841637. S2CID 22440127.
  7. Shawky, R. M., Elsayed, S. M., & Amgad, H. (2016). Autosomal recessive ichthyosis with limb reduction defect: A simple association and not CHILD syndrome. Egyptian Journal of Medical Human Genetics, 17(3), 255-258.
  8. Cicely Blair (February 1976). "The action of a urea—lactic acid ointment in ichthyosis". British Journal of Dermatology. 94 (2): 145–153. doi:10.1111/j.1365-2133.1976.tb04363.x. PMID 943169. S2CID 29854858.
  9. Sundberg, John P., Handbook of Mouse Mutations with Skin and Hair Abnormalities, Page 333, Published by CRC Press, 1994, ISBN 0-8493-8372-2
  10. Gross, Thelma Lee, Veterinary Dermatopathology, Page 174-179, Published by Blackwell Publishing, 2004, ISBN 0-632-06452-8
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