Standard 2-dimensional (2D) frontal and lateral facial photographs will be taken of the same XLHED-affected male subjects as well as of adult females (ages 18-45 yrs) at risk for being XLHED carriers and unaffected adult female controls. The 2D facial photographs will serve a dual purpose; the first being to beta-test a previously developed algorithm to identify males affected with XLHED (Automatic Phenotype Identification of XLHED Patients Final Report, December 25, 2012, unpublished), and the second to adapt the facial recognition algorithm to identify female carriers of XLHED.