AQP5 and epidermolytic palmoplantar keratoderma, 1: Blaydon et al. described five different missense AQP5 variants in twelve families with palmoplantar keratoderma from Great Britain, Scotland, and Sweden in 2013 [11], including Swedish families from the coasts of the Bothnian bay of the Baltic Sea, in which this PPK type was first described [12].