Harlequin ichthyosis is an extremely rare form of ichthyosis and the most severe. The newborn child is covered with plates of thick skin that crack and split apart. The thick skin plates can pull at and distort facial features. The tightness of the skin pulls around the eyes and the mouth, forcing the eyelids and lips to turn inside out, revealing the red inner linings. The chest and abdomen of the infant may be severely restricted by the tightness of the skin, making eating and breathing difficult. The hands and feet may be small, swollen, and partially flexed. The ears may appear to be misshapen or missing, but are really fused to the head by the thick skin. Harlequin infants need to be cared for in the neonatal intensive care unit immediately.
Premature birth is typical, leaving infants at risk for complications from early delivery. These infants are also at high risk for difficulty breathing, infection, low body temperature, and dehydration. Constriction and swelling of the mouth may interfere with the suck response and infants may need tube feeding. Medical monitoring is difficult because of the abnormal skin; electrodes cannot be placed effectively and blood vessels cannot be seen under the skin. Placing lines in the artery and vein of the umbilical cord can aid in monitoring the infant and delivering fluids and nutrition. These infants may have problems maintaining normal levels of electrolytes, especially sodium in their blood. They are particularly prone to develop hypernatremia (high sodium levels in the blood). The baby’s corneas need to be lubricated and protected if the eyelids are forced open by the tightness of the skin. A high, humidity environment in a heated incubator is necessary to help maintain body temperature and to prevent the skin from cracking.
The thick plate-like skin will gradually split and peel off. Antibiotic treatment may be necessary to prevent infection at this time. Administration of oral etretinate (1 mg./kg. body weight) may accelerate shedding of the thick scales. Most harlequin infants will need one-on-one nursing care for the first several weeks of life.
In the past, these infants rarely survived the first few days of life. However, with recent advances in neonatal care and perhaps with the administration of etretinate
, 1 mg./kg. body weight, harlequin infants can survive. Several surviving children are now in their teenage years, with several in their twenties. The surviving children display dry, reddened skin, which may be covered by large thin scales, and sparse hair. Physical development may be delayed by the enormous calorie needs their skin function demands, but mental and intellectual developments are expected to be normal. Harlequin ichthyosis demands a meticulous skin care regimen to keep the skin moisturized and pliable and to prevent cracking and fissuring that may lead to infection.
Harlequin ichthyosis is a recessively inherited disorder. Individuals must inherit two recessive genes in order to show the disease, one from each parent, but the parents (“carrier”) show no signs of the ichthyosis. (For more information on the genetics of harlequin ichthyosis refer to FIRST's publication, Ichthyosis: The Genetics of Inheritance.
 It takes a week or two for etretinate to work loosening the scales. Because most of the fatalities from this condition occur in the first few days of life, many of the successes attributed to etretinate use in the medical literature may be equally due to the high quality of care in the immediate newborn period and to a less severely affected newborn. Some newborns with Harlequin ichthyosis will not survive, even with the best of care, because of the severity of their condition.
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