The Tricho-Hepato-Enteric (THE) syndrome is an autosomal recessive condition marked by early and intractable diarrhea, hair abnormalities, and immune defects. Mutations in TTC37, which encodes the putative protein Thespin, have recently been associated with THE syndrome. In this article, we extend the pattern of TTC37 mutations by the description of 11 novel mutations in 9 patients with a typical THE syndrome. The mutations were spread along the gene sequence, none of themrecurrent. Different types of mutation were observed: frameshift mutations, splice-site altering mutations, or missense mutations, most of them leading to the creation of a premature stop codon. Concurrently, we investigated the pattern of TTC37 expression in a panel of normal human tissues and showed that this gene is widely expressed, with high levels in vascular tissues, lymph node, pituitary, lung, and intestine. In contrast, TTC37 is not expressed in the liver, an organ that is not consistently affected in THE syndrome. Last, we suggested a model for the putative structure of the unknown Thespin protein. Hum Mutat 32:277-281, 2011. (C) 2011 Wiley-Liss, Inc.