Pseudoxanthoma elasticum and polyposis coli: a novel co-mutation.

Pseudoxanthoma elasticum and polyposis coli are inherited conditions not, to our knowledge, previously reported to coexist. The spontaneous appearance of both conditions in a 62-year-old woman may represent a novel mutation. The defective cell in both pseudoxanthoma and some of the extracolonic manifestations of Gardner's syndrome is the fibroblast; therefore, this case may represent a unique variation of Gardner's syndrome.