Apparent non-penetrance for dystopia in Waardenburg syndrome type I, with some hints on the diagnosis of dystopia canthorum.
Two large pedigrees with Waardenburg syndrome type I (W--I), i.e. with dystopia canthorum and blepharophimosis, are described to show both the variable expressivity of dystopia canthorum, which may be confused with non-penetrance of this sign, and the possibility to firmly diagnosis it with the new biometric index W, which differentiates a dystopic from a non-dystopic or a non-apparent dystopic subject,  the latter within a defined biometric range. A general discussion of the relative value of blepharophimosis and dystopia canthorum as diagnostic features in W--I is presented, to conclude on the greater value of dystopia canthorum, which can be identified with confidence in more than 96% of carriers. Empirical probabilities are given for dystopia canthorum and blepharophimosis in the general populations, based on data from the world literature, useful for all ethnic groups.
D000015:Abnormalities, Multiple / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005143:Eyelids / Q000002:abnormalities*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D014849:Waardenburg Syndrome / Q000235:genetics*