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Harlequin type ichthyosis
Harlequin-type ichthyosis (also harlequin ichthyosis, ichthyosis congenita, or keratosis diffusa fetalis), a skin disease, is the most severe form of congenital ichthyosis, characterized by a thickening of the keratin layer in fetal human skin. In sufferers of the disease, the skin contains massive, diamond-shaped scales, and tends to give off a reddish color. In addition, the eyes, ears, mouth, and other appendages may be abnormally contracted. The scaly keratin greatly limits the child's movement. Because the skin is cracked where normal skin would fold, it is easily pregnable by bacteria and other contaminants, resulting in 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-shape of the scales (resembling the costume of Arlecchino), which are caused by severe hyperkeratosis. The disease can be diagnosed in the uterus by way of fetal skin biopsy or by morphologic analysis of amniotic fluid cells obtained by amniocentesis. In addition, doctors can now usually recognize common features of the disease through ultrasound, and follow up with 3D ultrasound can diagnose the condition.
Additional recommended knowledge
The disease has been known since around 1750, and was first described in the diary of Rev. Oliver Hart:
Over a hundred cases have been reported worldwide in modern times. Neither gender nor ethnicity seem to affect the likelihood of a child having the disorder. A disproportionately high number of children have consanguineous parents. Those from families with a history of severe skin disorders may have a higher risk of birthing a harlequin child.
The features of sufferers are deformed facially and cranially. The ears may be very poorly developed or absent entirely, as may the nose. The eyelids are severely everted (ectropion), 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 wide grimace (Eclabium). Arms, feet, and fingers are almost always deformed in such a way that they cannot bend properly, and may be below the normal size. They present Hypoplasia in the fingers, therefore, they cannot grab things properly, or they can barely touch them. 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 armor-like 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.
Treatment and prognosis
In the past, the disorder was invariably fatal, whether due to dehydration, infection (sepsis), restricted respiration due to the plating, or other related causes. The most common cause of death was systemic infection and sufferers rarely survived for more than a few days. However there have been improvements in care, most notably the drug Isotrex. Some patients have survived into adolescence and, in very rare cases, lived to adulthood.
A Real Families documentary broadcast on ITV1 in the United Kingdom in 2005 (and later rebroadcast in other countries) showed the lives of two pairs of sisters afflicted with the condition: Lucy and Hannah Betts (ages 18 and 15), and Dana and Lara Bowen (ages 8 and 1½). The girls all went through a daily routine of getting up early in the morning and bathing for two hours to soften the skin, scrubbing hard to remove as much of the hard extra skin as possible, and then covering their entire bodies in a thick layer of moisturiser. A second and third "creaming" as they called it had to be performed in the afternoon and at bedtime to soften the skin. Even with this treatment a thick layer of hyperkeratotic skin covered them and they were plagued with infections. Scales on the inside of the eyelids had blinded one of Lucy's eyes and left the other eye with 10% vision. Hannah Betts also suffers from cerebral palsy. Their skin was said to grow at fourteen times the normal rate. Vacuuming the carpets was necessary at least a couple of times a day to remove the shed skin.
The children were said to be four of just seven in the United Kingdom, Lucy being the longest surviving of any such child in the country ever. The chances of suffering from the condition were given as roughly one in a million in general, and exactly one in four in families already with one such child. These figures would indicate that one in 500 people have the recessive allele, giving a one-in-250,000 chance of two unrelated people bringing these allele together, and finally there being a one-in-four chance of these alleles being brought together and causing the condition.
The chances of any one person with the disease producing a child who is also a sufferer would be very high - about 1 in 2000.
In San Diego a young man, Ryan González, has this condition and has not only survived to adulthood but also thrives as a triathlete. His treatment involves dosing with isotretinoin (also known as Accutane), the constant use of lotions to keep the skin supple, and use of a very high-caloric diet of at least 7,500 calories a day, including a nightly feeding tube of pure protein due to the constant shedding of his skin, which is believed to shed seven to ten times faster than unaffected skin.
Ryan takes part in the triathlon for athletes with disabilities and swims regularly.
Mutations in the ABCA12 gene cause 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 recessive pattern, 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.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Harlequin_type_ichthyosis". A list of authors is available in Wikipedia.|