COVER FIGURE: XL-HED subjects show a decrease in palmar sweat ducts and produce little to no sweat (a,b). Quanti. cation of the number of palmar sweat ducts shows that XL-HED subjects have few sweat ducts compared to controls (c). Graph of the sweat volumes (d) collected over 30 minutes shows XL-HED subjects produced little to no sweat. See article by Jones et al. in this issue.