Keratitis-Ichthyosis-Deafness (KID) syndrome
KID syndrome, first described in 1915, is a rare genetic multi-system disorder. Only about a hundred cases have been published. Based on a review of many articles in the medical literature, it appears that all cases of KID syndrome have skin findings, which include red and rough, thickened plaques that are sometimes scaling, as well as sensorineural deafness or severe hearing impairment. In addition, 95% of patients developed eye findings, predominantly keratitis (inflammation of the cornea), which may manifest with photophobia (the eyes are very sensitive to light). A few percent of patients had only recurrent or chronic conjunctivitis (inflammation of the mucous membrane of the eye). Sparse hair or alopecia (baldness) is also quite common. The skin of the palms and soles is affected in about 95% of all patients, while 77% have absent or dystrophic (abnormal) nails. There is a whole spectrum of other associated abnormalities, including recurrent infections, abnormal teeth, reduced sweating, growth or mental delay, which may occur in some but not many patients. The clinical presentation may vary greatly between patients and may change over time. Due to the involvement of several organ systems and the potential impairment of hearing, speech, and sight, patients usually require multidisciplinary treatment.
KID syndrome is a genetic disorder and can be transmitted from a parent to a child in an autosomal dominant fashion. That means that each individual affected with the disease would have one abnormal and one normal copy of the disease gene. When, by chance, the abnormal gene copy is passed on to the offspring, the child will be affected. When the normal gene copy is transmitted, the child will be unaffected. The risk for an individual with KID syndrome to have an affected child is 50% for each pregnancy. Nevertheless, nine out of ten patients carry a new, spontaneously occurring mutation that is not present in either parent.
The research laboratory of Dr. G. Richard at the Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia, PA discovered the gene whose mutations cause KID syndrome. It is called gap junction protein beta 2 (GJB2) and located on the long arm of human chromosome 13. This gene encodes the structural protein ‘connexin-26’ (Cx26), which forms gap junction channels that connect neighboring cells and permit the exchange of small molecules and ions. To date is known that about 80% of KID patients carry a common mutation replacing an aspartic acid residue at position 50 of Cx26 with an asparagine. The remainder of patients usually harbors unique mutations. It is thought that the protein made from the abnormal gene copy interferes with the assembly of gap junctions and the function of normal Cx26 in a so-called ‘dominant negative’ manner. Hence the direct cell-cell communication in the skin and other tissues, such as cornea and inner ear, might be impaired. Nevertheless, the exact pathomechanisms leading to KID syndrome are still not fully understood and are subject of current and future research.
Individuals diagnosed with KID syndrome or related disorders are eligible for enrollment in genetic research studies at the Richard laboratory. Information may be requested at the address below.
1) Caceres-Rios H, Tamayo-Sanchez L, Duran-Mckinster C, de la Luz Orozco M, Ruiz-Maldonado R: Keratitis, ichthyosis, and deafness (KID syndrome): review of the literature and proposal of a new terminology. Pediatr Dermatol 13:105-113, 1996
2) Richard G, Rouan F, Willoughby CE, et al.: Missense mutations in GJB2 encoding connexin-26 cause the ectodermal dysplasia keratitis-ichthyosis-deafness syndrome. Am J Hum Genet 70:1341-1348, 2002
3) Szymko-Bennett YM, Russell LJ, Bale SJ, Griffith AJ: Auditory manifestations of Keratitis-Ichthyosis-Deafness (KID) syndrome. Laryngoscope 112:272-280, 2002
4) van Steensel MA, van Geel M, Nahuys M, Smitt JH, Steijlen PM: A novel connexin 26 mutation in a patient diagnosed with keratitis- ichthyosis-deafness syndrome. J Invest Dermatol 118:724-727, 2002
5) Tuppurainen K, Fraki, J, Karjalainen S, Paljarvi L, Suhonen R, Ryynanen M: The KID syndrome in Finland. Acta Opththalmol (Copenh) 66:692-698, 1988
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