Keratitis ichthyosis deafness (KID) syndrome is a rare, genetic, multi-system disorder. It is characterized by defects of the surface of the corneas (keratitis), red, rough thickened plaques of skin (erythrokeratoderma) and sensorineural deafness or severe hearing impairment. The skin on the palms of the hands and soles of the feet and the nails may be affected. KID syndrome belongs to a group of skin disorders marked by dry, scaly skin known as the ichthyoses. KID syndrome is inherited as an autosomal dominant trait.
KID syndrome is present at birth. Nearly all cases have skin involvement, which includes red, rough, thickened plaques that are sometimes scaling, as well as sensorineural deafness or severe hearing impairment.
Most patients develop eye findings, predominantly keratitis (superficial defects of the cornea), which may result in the eyes being very sensitive to light (photophobia), small blood vessels growing from the iris over the cornea (neovascularization), and progressive decline of vision. A small percentage of patients may have recurrent or chronic inflammation of the mucous membrane of the eye (conjunctivitis).
Sparse hair or areas of baldness (alopecia) are relatively common, while a complete lack of hair is rare. The palms of the hands and soles of the feet have thickened hardened skin in most patients, while a smaller percentage may have absent or abnormal nails.
There is a whole spectrum of other associated symptoms, including recurrent infections, abnormal teeth, reduced sweating, and an increased risk for developing squamous cell carcinoma of the skin or mucous membranes, which may occur in some but not many patients. A very small percentage of patients encounter life-threatening infections during the neonatal period.
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 will have one abnormal gene for the disease and one normal 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 adult with KID syndrome to have an affected child is 50% for each pregnancy. Nevertheless, approximately nine out of ten patients carry a new, spontaneously occurring mutation that is not present in either parent.
The gene whose mutation causes KID syndrome is called gap junction protein beta 2 (GJB2) and is located on the long arm of human chromosome 13 (13q11-q12). 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. The impairment of this connection and exchange may affect direct cell-to-cell communication in the skin and other tissues, such as the cornea and inner ear. Very rarely, KID syndrome with congenital absence of hair, may be caused by mutations in the gene GJB6 encoding the gap junction protein beta 6, also known as “connexin-30,” which fulfills similar functions as connexin-26.
Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Pairs of human chromosomes are numbered from 1 through 22, and an additional 23rd pair of sex chromosomes which include one X and one Y chromosome in males and two X chromosomes in females. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 13q11-q12” refers to bands 11-12 on the long arm of chromosome 13. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
KID syndrome appears to affect females slightly more often than males. The disorder is very rare with fewer than 100 cases reported in the medical literature. Collectively, the ichthyoses affect more than 1,000,000 people in the United States.
Individuals with KID syndrome usually require multidisciplinary treatment due to the involvement of several organ systems and the potential impairment of hearing, speech, and sight.
The skin symptoms of KID syndrome can be treated by applying skin softening emollients. This can be particularly effective after bathing while the skin is still moist. Lotions containing alpha-hydroxy acids can be an effective treatment for scaling skin. Cholesterol or ceramide containing emollients may also improve the scaling.
Genetic counseling may be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.
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