Harlequin type ichthyosis

Image:Harlequin2.jpg

Harlequin type ichthyosis (also harlequin ichthyosis, ichthyosis congenita, or keratosis diffusa fetalis), the most severe form of congenitalichthyosis, is characterized by a thickening of the keratinlayer in fetalhumanskin, appearing as massive, diamond-shaped scales. In addition, the eyes, ears, mouth, and other appendages may be abnormally contracted. The scaly keratin limits the child's movement, and because it is cracked where normal skin would fold, it is easily pregnable by bacteriaand other contaminants, resulting in a serious risk of fatal infection.

Sufferers are known as harlequin fetuses, harlequin babies, or harlequins.

The harlequin type designation comes from both the baby's apparent facial expression and the diamond-shapeof the scales (resembling the costume of Arlecchino), which are caused by severe hyperkeratosis. Seventeenth centuryentertainersknown as jesters, or harlequins, wore costumeswith diamond patterns on them, as well as a particular style of face paint. The features of the harlequin fetus resemble this stylized makeup, and their faces are often pulled tight into grim parodies of a clown's smile. The disease can be diagnosedin the wombby way of fetal skin biopsy.

Features

The features of sufferers are very deformed. The ears may be very poorly developed or absent entirely, as may the nose. The eyelidsare severely inverted, which leaves the eyes and the area around them very susceptible to trauma. They often bleed upon birth. The lips, pulled by the dry skin, are fixed into a vestige of a clown's smile, which many find extremely disconcerting. Arms, feet, and fingersare almost always deformed in such a way that they cannot bend properly, and may be below the normal size. Polydactyly, a condition in which one has more than the usual number of toes or fingers, has also been found in these infants.

They are extremely susceptible to changesin temperaturedue to their plated skin, which prevents normal heat loss. This can result in hyperthermia. Their respiration is also restricted by the skin, which impedes the chest wall from expanding and drawing in enough air. This can lead to hyperventilationand respiratory failure. Harlequins are often dehydrated, as their plated skin is not well suited to keeping waterin.

Treatment and prognosis

In the past, the disorder was invariably fatal, whether due to dehydration, infection, restricted respirationdue to the armored plating, or other related causes. The most common cause of death is systemic infection. Therefore, practically all children did not survive for longer than a few days. However, there have been improvements in care, and some children have survived into adolescence and, in very rare cases, to adulthood; one has even become a triathlete [1]. Because of this, the terms harlequin baby or just harlequin are now preferred over harlequin fetus. Treatment involves dosing with isotretinoin, the constant use of lotions to keep the skin supple, and use of a very high-calorie diet, including a feeding tube, required by the constant shedding of the skin, believed to shed seven to ten times faster than unaffected skin.

Genetics

Mutations in the ABCA12genecause harlequin ichthyosis. The ABCA12 gene makes a protein that is essential for the normal development of skin cells. Although the protein's exact function is unknown, researchers believe that it probably plays a major role in the transport of lipids (fats) in the outermost layer of skin (the epidermis). Mutations in the ABCA12 gene lead to the production of an abnormally small version of the protein that cannot transport lipids properly. The loss of functional ABCA12 protein disrupts the normal development of the epidermis, preventing the skin from forming an effective barrier and resulting in the hard, thick scales characteristic of harlequin ichthyosis.

This condition is likely inherited in an autosomal recessivepattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

History

The disease has been known since around 1750, and was first described in the diary of Rev. Oliver Hart:

"On Thursday, April ye 5, 1750, I went to see a most deplorable object of a child, born the night before of one Mary Evans in 'Chas'town. It was surprising to all who beheld it, and I scarcely know how to describe it. The skin was dry and hard and seemed to be cracked in many places, somewhat resembling the scales of a fish. The mouth was large and round and open. It had no external nose, but two holes where the nose should have been. The eyes appeared to be lumps of coagulated blood, turned out, about the bigness of a plum, ghastly to behold. It had no external ears, but holes where the ears should be. The hands and feet appeared to be swollen, were cramped up and felt quite hard. The back part of the head was much open. It made a strange kind of noise, very low, which I cannot describe. It lived about forty-eight hours and was alive when I saw it."

More than a hundredcases have been reported worldwide in modern times. Neither sexnor raceseem to change the likelihood of a child having the disorder. A disproportionately high number of children have consanguineousparents. Those from families with a history of severe skin disorders may have a higher risk of birthing a harlequin child.

Internet

Babies afflicted with this disease have a most unusual appearance, which many find distressing. For this reason, websites with photographs of such babies are often linked to on Internet forumsby Internet trollsas a form of shock site, even though many are medical websites and not intended for this purpose. Some of these photos have been included in the notorious Pain Seriesof shock image collages. A series of photos claiming to show the effects of depleted uraniumin Iraqincludes a picture of a child with harlequin ichthyosis. Critics of the photos question whether the photo was from Iraq, let alone whether the case was caused by depleted uranium.

References

• Sheila Au, MD, Julie Prendiville, MD. (2004). eMedicine Specialties > Dermatology > Pediatric Diseases. Retrieved Jan. 20, 2004 from http://www.emedicine.com/derm/topic192.htm
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External links

• A Case Of Harlequin Fetus With Psoriasis In His Family. Article from the Internet Journal of Pediatrics and Neonatology. (Warning: Includes graphic photographs that might offend some viewers.)
• Harlequin Ichthyosis(Warning: Not a medical site - includes photographs displayed as a curiosity.)
• BBC News story: Key to severe skin disease found
• Medical Article
• Story of teenager with Harlequin type ichthyosis

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Harlequin+type+ichthyosis Wikipedia article Harlequin type ichthyosis.