1. Department of Pediatrics The University of Pennsylvania Philadelphia 19104 Pennsylvania
2. Division of Genetics The Children's Hospital of Philadelphia Philadelphia 19104 Pennsylvania
3. Division of Biochemical Genetics The Children's Hospital of Philadelphia Philadelphia 19104 Pennsylvania
4. Department of Biochemistry and Biophysics and Graduate Group in Biochemistry and Molecular Biophysics The University of Pennsylvania Philadelphia 19104 Pennsylvania
5. Department of Pathology The University of Pennsylvania Philadelphia 19104 Pennsylvania
6. Department of Medical and Molecular Genetics King's College London London United Kingdom
7. St. John's Institute of Dermatology King's College London London United Kingdom
8. The Centre for Dermatology and Genetic Medicine University of Dundee Dundee United Kingdom