Variable expressivity and novel PTEN mutations in Cowden syndrome

Cowden syndrome (CS) is a phosphatase and tensin homolog gene (PTEN)-associated condition characterized by multiple mucocutaneous hamartomas and an increased risk of malignancies. We reported an isolated case and another of several individuals in one family affected by CS. The isolated case showed typical features, including fibrocystic breast disease, benign thyroid nodules, and multiple papillomatous lesions in the face and oral cavity, and the cause was a novel nonsense mutation-guanine (G) to thymine (T) transition at position 940 (c.940 G>T)-in PTEN. In the family, the proband showed erythema nodosum, duodenal ulcer, intestinal polyps, cervical lipoma, renal cysts, and glaucoma, whereas multiple members of her family were found to have intestinal polyps, and a sister had been diagnosed with breast cancer at early age. An intronic mutation-T>G transition at the +32 position of intron 8 (c.1026+32 T>G)-was found in this family, with in silico analysis revealing the creation of a new donor splice site. This study confirmed the involvement of PTEN in CS and the variable clinical expressivity of disease.