Cowden disease (CD) is a rare autosomal dominant disease with variable expression, affecting a number of systems in the form of multiple hamartomatous neoplasms of ectodermal, mesodermal, and endodermal origin¹ (multiple hamartoma neoplasia syndrome). CD usually presents in late adolescence and is caused by a germ mutation in the PTEN gene.² Classically, the mucocutaneous features of CD are tricholemmomas, oral fibromas, acral keratoses, palmar pits, and gingival and palatal papules. These mucocutaneous signs are important markers for systemic findings; in particular breast carcinoma (20%), which is often bilateral,^3,4 thyroid carcinoma (8%) and endometrial carcinomas.² Various manifestations of the central nervous system (mental retardation,⁵ seizures, ganglinoneuromas), musculoskeletal system (craniomegaly, kyphoscoliosis and high arched palate) and gastrointestinal system (multiple hamartomatous polyps, adenocarcinomas arising in the polyps) are well documented. In addition, ovarian cysts and menstrual abnormalities are known to occur in the female genital tract.⁶

Bannayan–Ruvalcaba–Riley syndrome has many clinical features in common with CD, including mucocutaneous manifestations and an increased risk of gastrointestinal polyps and malignancy. …