Waardenburg syndrome: A genetic disorder that causes deafness, white forelock (a frontal white blaze of hair), a difference of color between the iris of one eye and the other (heterochromia iridis), white eye lashes, and wide-set inner corners of the eyes.
The deafness is typically congenital (present at birth), bilateral, profound sensorineural (nerve) deafness. The severity of Waardenburg syndrome (WS) varies and about 40 percent of affected persons escape the deafness. The white forelock may be present at birth. The majority of individuals with WS have the white forelock or early graying of the scalp hair before age 30.
WS is inherited in an autosomal dominant manner in which the heterozygous state (with one copy of the gene) is sufficient to cause the syndrome. The homozygous form of WS with two copies of the gene is a very severe (and fortunately rare) disorder with very severe upper-limb defects that has been called the Klein-Waardenburg syndrome.
The gene for classic WS, symbolized WS1, is on chromosome 2 (in band q35) and is the PAX3 gene which encodes a DNA-binding transcription factor that is expressed in the early embryo. The syndrome is named for a Dutch eye doctor named Petrus Johannes Waardenburg (1886-1979) who first noticed that people with differently colored eyes often had a hearing impairment.