Autosomal dominant diffuse non-epidermolytic palmoplantar keratoderma (NEPPK) is a clinically and genetically heterogeneous disorder, one form of which is associated with a whitish spongy appearance upon immersion in water (MIM 600231). Using linkage data in combination with whole-exome sequencing in families with NEPPK, heterozygosity for 5 different missense mutations in AQP5 (encoding aquaporin-5) was identified recently in affected members of 7 Swedish families, 3 British families, and a Scottish family.(1,2) All the mutations segregated with disease in the respective families and were not found in the dbSNP or 1000 Genomes Project databases. A further gain-of-function mutation in AQP5 was subsequently reported in a large NEPPK pedigree of Chinese Han descent.(3) This article is protected by copyright. All rights reserved.