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What Is Harlequin Ichthyosis?
Harlequin ichthyosis is a severe genetic disorder that mainly affects the skin. Infants with this condition are born with very hard, thick skin covering most of their bodies. The skin forms large diamond-shaped plates separated by deep cracks (fissures). These skin abnormalities affect the shape of the eyelids, nose, mouth and ears, and restrict movement of the arms and legs. Restricted movement of the chest can lead to breathing difficulties and respiratory failure.
The skin normally forms a protective barrier between the body and its surrounding environment. The skin abnormalities associated with harlequin ichthyosis disrupt this barrier, making it more difficult for affected infants to control water loss, regulate their body temperature and fight infections. Infants with harlequin ichthyosis often experience an excessive loss of fluids from the body (dehydration) and develop life-threatening infections during the newborn period.
How Common Is Harlequin Ichthyosis?
Harlequin ichthyosis is very rare; its exact incidence is unknown.
What Genes Are Related to Harlequin Ichthyosis?
The ABCA12 gene makes a protein that is essential for the normal development of skin cells. This protein appears to play a major role in the transport of lipids (fats) in the outermost layer of skin (the epidermis). Some mutations in the ABCA12 gene prevent the cell from making any ABCA12 protein. Other mutations 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.
How Do People Inherit 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.
What Other Names Do People Use for Harlequin Ichthyosis?
· Harlequin baby syndrome
· HI
· Ichthyosis Congenita, Harlequin Fetus Type
References
1. Akiyama M, Sakai K, Sugiyama-Nakagiri Y, Yamanaka Y, McMillan JR, Sawamura D, Niizeki H, Miyagawa S, Shimizu H. Compound Heterozygous Mutations Including a De Novo Missense Mutation in ABCA12 Led to a Case of Harlequin Ichthyosis with Moderate Clinical Severity. J Invest Dermatol. 2006 Jul;126(7):1518-23. Epub 2006 May 4.
2. Akiyama M, Sugiyama-Nakagiri Y, Sakai K, McMillan JR, Goto M, Arita K, Tsuji-Abe Y, Tabata N, Matsuoka K, Sasaki R, Sawamura D, Shimizu H. Mutations in lipid transporter ABCA12 in harlequin ichthyosis and functional recovery by corrective gene transfer. J Clin Invest. 2005 Jul;115(7):1777-84.
3. Akiyama M. The pathogenesis of severe congenital ichthyosis of the neonate. J Dermatol Sci. 1999 Sep;21(2):96-104. Review.
4. Gene Review: Autosomal Recessive Congenital Ichthyosis
5. Hovnanian A. Harlequin ichthyosis unmasked: a defect of lipid transport. J Clin Invest. 2005 Jul;115(7):1708-10. Review.
6. Kelsell DP, Norgett EE, Unsworth H, Teh MT, Cullup T, Mein CA, Dopping-Hepenstal PJ, Dale BA, Tadini G, Fleckman P, Stephens KG, Sybert VP, Mallory SB, North BV, Witt DR, Sprecher E, Taylor AE, Ilchyshyn A, Kennedy CT, Goodyear H, Moss C, Paige D, Harper JI, Young BD, Leigh IM, Eady RA, O'Toole EA. Mutations in ABCA12 underlie the severe congenital skin disease harlequin ichthyosis. Am J Hum Genet. 2005 May;76(5):794-803. Epub 2005 Mar 8.
7. Moskowitz DG, Fowler AJ, Heyman MB, Cohen SP, Crumrine D, Elias PM, Williams ML. Pathophysiologic basis for growth failure in children with ichthyosis: an evaluation of cutaneous ultrastructure, epidermal permeability barrier function, and energy expenditure. J Pediatr. 2004 Jul;145(1):82-92.