Harlequin type ichthyosis

Harlequin type ichthyosis, the most severe form of congenital ichthyosis, is characterized by a thickening of the keratin layer in fetal skin. The afflicted child is born not with skin, but massive, diamond-shaped scales. As well, the eyes, ears, mouth, and other appendages can be abnormally contracted. The scaly armor limits the child's movement, and because it is cracked where normal skin would fold, it is useless for skin's primary function -- protection. Bacteria and other contaminants easily pass into the cracks and can cause lethal infections.

The term comes from both the baby's facial expression and the diamond-shaped pattern of the scales (resembling the costume of Arlecchino), which are caused by severe hyperkeratosis. Seventeenth century entertainers known as jesters, or harlequins, wore costumes with 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 is also known as harlequin ichthyosis, ichthyosis congenita, and keratosis diffusa fetalis. Sufferers are known as harlequin fetuses, harlequin babies, or plain harlequins.

The underlying genetic and biochemical abnormalities that result in harlequin ichthyosis are caused by mutation in the gene ABCA12, the protein encoded by this gene is is essential for the normal development of skin cells, but its role in the process is not understood. The disorder is most likely inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. The disease can be diagnosed in the womb by way of fetal skin biopsy.

In the past, the disorder was invariably fatal, whether due to dehydration, infection, restricted respiration due 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] (http://www.10news.com/health/3919722/detail.html). 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.

The features of sufferers are very deformed. The ears may be very poorly developed or absent entirely, as may the nose. The eyelids are severely everted, 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 fingers are 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 changes in temperature due 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 hyperventilation and respiratory failure. Harlequins are often dehydrated, as their plated skin is not well suited to keeping water in.

The disease has been known since around 1750, and first described 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 hundred cases have been reported internationally in modern times. Neither gender nor race seems to make a difference in likelihood of a child having the disorder. Those with families with a history of severe skin disorders may have a higher risk of birthing a harlequin child. Notably, Harlequin ichthyosis has been documented in southern Iraq, where it may be caused by mother's exposure to radioactive uranium oxide dust during early pregnancy.

Websites with photographs of children affected by this disease are often linked to on Internet forums by Internet trolls as a form of shock site, even though many are medical websites and not intended for this purpose. The tactic is quite effective as the results of the disease are very unusual-looking and often disturbing. Some of these photos have been included in the notorious Pain Series of shock image collages.

External links

• A Case Of Harlequin Fetus With Psoriasis In His Family (http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijpn/vol2n1/harlequin.xml). Article from the Internet Journal of Pediatrics and Neonatology. (includes graphic photographs)
• Harlequin Ichthyosis (http://asylumeclectica.com/malady/archives/harlequin.htm) (not a medical site)
• BBC News story: Key to severe skin disease found (http://news.bbc.co.uk/2/hi/health/4337009.stm)

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