E P Prens1, H H van der Zee2, J D Laman3. 1. Department of Dermatology, Erasmus University Medical Center Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam, the Netherlands. e.prens@erasmusmc.nl. 2. Department of Dermatology, Erasmus University Medical Center Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam, the Netherlands. 3. Department of Neuroscience, University Medical Center Groningen, University of Groningen, P.O. Box 196, 9713 AV, Groningen, the Netherlands.