Classic CAH, the disorder targeted by newborn screening programs, is caused by a deficiency of the enzyme steroid 21-hydroxylase, and comes in two forms - simple virilizing and a salt-wasting form. Incidence of CAH can vary greatly between populations. The highest reported incidence rates are among the Yupic Eskimos of Alaska (1:280) and on the French island of Réunion (1:2100).[11]