NORD gratefully acknowledges François Lagacé, MD Candidate, McGill University School of Medicine, and Edel O’Toole, MB, PhD, FRCP, Professor of Molecular Dermatology, Centre Lead, Queen Mary University of London, for assistance in the preparation of this report.
Harlequin ichthyosis is a rare genetic skin disorder. The newborn infant is covered with plates of thick skin that crack and split apart. The thick plates can pull at and distort facial features and can restrict breathing and eating. Harlequin infants need to be cared for in the neonatal intensive care unit immediately. Harlequin ichthyosis is inherited in an autosomal recessive pattern.
Infants with Harlequin ichthyosis are covered in thick plate-like scales of skin. 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 breathing and eating difficult. The hands and feet may be small and swollen, and partially flexed. The ears may appear to be misshapen or missing, but are really fused to the head by the thick skin. Infants born with harlequin ichthyosis may also have a flat nose (depressed nasal bridge), abnormal hearing, frequent respiratory infections, and decreased joint mobility.
Premature birth is typical, leaving the infants at risk for complications from early delivery. These infants are also at high risk for low body temperature, dehydration, and hypernatremia (elevated levels of sodium in the blood). Constriction and swelling of the mouth may interfere with the suck response and infants may need tube feeding. The baby’s corneas need to be lubricated and protected if the eyelids are forced open by the tightness of the skin.
Harlequin ichthyosis is caused by changes (mutations) in the ABCA12 gene, which gives instructions for making a protein that is necessary for skin cells to develop normally. It plays a key role in the transport of fats (lipids) to most superficial layer of the skin (epidermis), creating an effective skin barrier. When this gene is mutated, the skin barrier is disrupted.
Harlequin ichthyosis is inherited in an autosomal recessive pattern. Recessive genetic disorders occur when an individual inherits an abnormal gene from each parent. If an individual receives one normal gene and one abnormal gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the abnormal gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier, like the parents, is 50% with each pregnancy. The chance for a child to receive normal genes from both parents is 25%. The risk is the same for males and females.
Harlequin ichthyosis affects males and females in equal numbers. This condition affects approximately one in 500,000 persons or about seven births annually in the United States.
Harlequin ichthyosis is diagnosed at birth based on the child’s physical appearance. Prenatal testing may be possible by testing fetal DNA for mutations in the ABCA12 gene. In addition, some of the features of harlequin ichthyosis maybe seen on ultrasound during the second trimester and onward.
A multi-disciplinary team is involved in the care of infants with harlequin ichthyosis as soon as they are born. This has been shown to improve outcomes and reduce complications such as respiratory distress, dehydration, electrolyte imbalances, impaired thermoregulation, systemic bacterial infections, and feeding difficulties. Early treatment with oral retinoids is also thought to improve outcomes. However, they are only used in severe cases due to their known toxicity and side effects.
The thick, plate-like skin of harlequin type ichthyosis will gradually split and peel off over several weeks. Antibiotic treatment may be necessary to prevent infection at this time. Administration of oral acitretin may accelerate shedding of the thick scales. Most harlequin infants will need one-on-one nursing care for the first several weeks of life.
After the thick plates peel off, the skin is left dry and reddened, and may be covered in large thin scales. The skin symptoms are treated by applying skin softening emollients. This can be particularly effective after bathing while the skin is still moist. Many patients with severe ichthyosis exfoliate manually by rubbing off the thick scale with special exfoliating gloves with a rough surface. Skin barrier repair formulas containing ceramides or cholesterol, moisturizers with petrolatum or lanolin, and mild keratolytics (products containing alpha-hydroxy acids or urea) can all work to keep the skin moisturized and pliable, and prevent cracking and fissuring that can lead to infection. Removal of damaged tissue (debridement) from the fingers may be needed if they are constricted by bands of skin to avoid a loss of circulation.
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Harlequin ichthyosis. Genetics Home Reference. Review Date: November 2008. 6pp. https://ghr.nlm.nih.gov/condition/harlequin-ichthyosis#genes Accessed May 1, 2019
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