Clouston syndrome (hidrotic ectodermal dysplasia) is an autosomal dominant ectodermal dysplasia characterized by alopecia, palmoplantar hyperkeratosis, and nail dystrophy. Recently, mutations in the GJB6 gene encoding the gap junction protein connexin 30 have been shown to cause this disorder. To date, all mutations have involved two codons: G11R and A88V. Here, we report a novel mutation V37E within the first transmembrane domain of connexin 30 in a spontaneous case of Clouston syndrome. The mutation was detected in genomic DNA, confirmed in reverse transcription polymerase chain reaction products, and was excluded from 100 ethnically matched control individuals by restriction enzyme analysis.