Waardenburg syndrome

Key tracking index: upward slanting eyes

Waardenburg syndrome is a genetic disorder that may be evident at birth (congenital). The range and severity of associated symptoms and findings may vary greatly from case to case. However, primary features often include distinctive facial abnormalities; unusually diminished coloration (pigmentation) of the hair, the skin, and/or the iris of both eyes (irides); and/or congenital deafness. More specifically, some affected individuals may have an unusually wide nasal bridge due to sideways (lateral) displacement of the inner angles (canthi) of the eyes (dystopia canthorum). In addition, pigmentary abnormalities may include a white lock of hair growing above the forehead (white forelock); premature graying or whitening of the hair; differences in the coloration of the two irides or in different regions of the same iris (heterochromia irides); and/or patchy, abnormally light (depigmented) regions of skin (leukoderma). Some affected individuals may also have hearing impairment due to abnormalities of the inner ear (sensorineural deafness).

For example, Waardenburg syndrome type I (WS1) is characteristically associated with sideways displacement of the inner angles of the eyes (i.e., dystopia canthorum), yet type II (WS2) is not associated with this feature. In addition, WS1 and WS2 are known to be caused by alterations (mutations) of different genes. --http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/430/viewFullReport

W-index
a = ICD (Inner Canthal Distance); Distance between inner corner of eyes

b = IPD (Interpupillary distance); Distance between the center of the pupils

c = OCD (Outer Canthal Distance); Distance between outer corner of eyes

x = (2a - (0.2119c + 3.909)) / c

y = (2a - (0.2479b + 3.909)) / b

W = x + y + a/b

W < 1.95 = abnormal

Images
http://commons.wikimedia.org/wiki/Category:Waardenburg_syndrome