An atypical presentation of a pathogenic STK11 gene variant in siblings not fulfilling the clinical diagnostic criteria for Peutz-Jeghers Syndrome.

Prepubertal gynaecomastia and prepubertal macro-orchidism (testicular enlargement without virilisation), always warrant endocrinological investigation, with PJS being an important differential diagnosis. Children may not fulfil the clinical criteria for a diagnosis of PJS at presentation. Genetic testing and gastroenterological investigation of parents may aid diagnosis.