1. Departments of Dermatology,
2. Department of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, U.K.,
3. School of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, U.K.,
4. Medical Research Council Cell Mutation Unit, University of Sussex, Falmer, Brighton BN1 9RR, U.K.
5. Paediatrics, University Hospital of Wales, Heath Park, Cardiff CF4 4XW, U.K.,