Letrozole effectively treats peripheral precocious puberty in a girl with McCune-Albright syndrome: a case report and review of the literature.

McCune-Albright syndrome (MAS) is a rare disorder caused by somatic GNAS gene mutations, characterized by peripheral precocious puberty (PPP), café-au-lait spots, and fibrous dysplasia of bone (FD). This case report details a 3-year-and-10-month-old girl presenting with vaginal bleeding, scattered café-au-lait spots, elevated estradiol (E2: 57 pg/mL), and a large right ovarian cyst (72 × 44 × 71 mm). Diagnostic evaluations confirmed gonadotropin-independent precocious puberty without central endocrine abnormalities. The patient was diagnosed with MAS and treated with letrozole (2.5 mg/day), an aromatase inhibitor, under close monitoring. Over 13 months, letrozole therapy resulted in complete resolution of vaginal bleeding and ovarian cysts, suppression of estrogen levels (E2 < 15 pg/mL), and stabilization of bone age progression. Height and weight remained within normal percentiles, with no adverse effects observed. This case underscores the efficacy and safety of letrozole in managing MAS-associated PPP, highlighting its role in delaying skeletal maturation and improving clinical outcomes. Early intervention and multidisciplinary monitoring are critical to optimize long-term prognosis in MAS patients.