Prepubertal gynaecomastia in a boy with Peutz-Jeghers syndrome: managing the aromatase overexpression

Background Gynaecomastia, although rarely related to testicular tumours, in boys with Peutz-Jeghers syndrome (PJS) usually occurs due to large-cell calcifying Sertoli cell tumour (LCCSCT). Case presentation A 4-year-old boy, with a genetic diagnosis of PJS, presented gynaecomastia since the age of 2, associated with increased height velocity (HV). He exhibited bilateral breast enlargement (Tanner-B4) and a testicular volume of 4 mL. Testicular ultrasound revealed multifocal microcalcifications in both testicles. A laboratory evaluation showed undetectable gonadotrophins, testosterone and oestrogen and inhibin A of 4.6 pg/mL (0.9–1.7). The boy was subjected to therapy with anastrozole. In the last follow-up, 2 years after the start of therapy, he experienced a less tense Tanner-B2 and a decrease in HV; serum inhibin A had become negative. Conclusions This is one of the most precocious PJS-related gynaecomastia treated with aromatase inhibitors (AIs) reported in the literature. Oestrogen levels, although under the detection limit, may be sufficient to stimulate breast tissue/growth plates. Inhibin A is a good marker of LCCSCT and an indicator of response to AIs.