1 Department of Dermatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
2 Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
3 Epithelial Genetics Group, Division of Molecular Medicine, Colleges of Life Sciences and Medicine, Dentistry and Nursing, University of Dundee, Dundee, UK.
4 Department of Dermatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. Electronic address: m.f.jonkman@umcg.nl.