Background. PTEN hamartoma tumor syndrome (PHTS) is an umbrella term including Cowden syndrome (CS), Bannayan-Riley-Ruvalcaba syndrome (BRRS), PTEN-related Proteus syndrome (PS), and PTEN-related Proteus-like syndrome. One of the disorders in PHTS spectrum, CS is characterized by macrocephaly, mucocutaneous findings, gastrointestinal system (GIS) polyposis and an increased lifetime risk of GIS, breast, thyroid and other cancers.

Case. In this study, we report an adolescent patient presenting with recurrent life-threatening upper GIS bleeding as a result of hamartomatous polyposis. Genetic studies revealed a known pathogenic nonsense mutation confirming the initial diagnosis of CS.

Conclusions. Additionally, we describe our therapeutic intervention to improve the patient`s clinical symptoms with sirolimus, which its use is infrequently addressed in the literature for pediatric age group harboring PTEN mutations.

Keywords: PTEN hamartoma tumor syndrome, PTEN mutation, gastrointestinal system bleeding, sirolimus