THU205 A Case Of Infant With Familial-Male Limited Precocious Puberty (FMPP) Inherited From Father Due To An Activating Mutation Of The Luteinizing Hormone/Chorionic Gonadotropin Receptor Gene

Disclosure: H. Yoo: None. J. Ha: None. M. Jung: None. Y. Choi: None. E. Yoo: None. We present an extremely rare case of FMPP with an activating mutation of the LHCGR gene in a Korean infant. A 16-month-old-boy was brought to the out-patient clinic with complaints of pubic hair, acne and rapid growth acceleration. His father had become aware of the symptoms 4 month before. His grandfather and father had a family history of precocious puberty and profound short stature (Height of grandfather and father: 148 cm and 158 cm respectively). At physical examination, his height was 83 cm (+1.2 SDS) and his weight was 14.3 kg (+2.8 SDS). The testicular volume was 2 mL and pubic hair was appropriate for Tanner stage 2. Stretched penile length was 7 cm (>2 SDS). He did not have any café au lait spots or hyperpigmentation. His bone age was significantly advanced to that of a 4 year old. Laboratory findings showed abnormally elevated serum testosterone (5.74 ng/mL) and slightly elevated α-fetoprotein (14.1 ng/ml; reference 0-10 ng/mL) with suppressed LH level (<0.07 mIU/mL). Serum levels of β-human chorionic gonadotropin, cortisol, 17-hydroxyprogesterone, androstenedione and dehydroepiandrosterone sulfate were within normal range. A gonadotropin releasing hormone (GnRH) stimulation test revealed a prepubertal response(peak LH 0.52). Brain magnetic resonance imaging study was reported to be normal. Ultrasound of the scrotum and adrenal gland were both normal. Due to the patient’s classic presentation and his family history of male-limited precocious puberty, a genetic analysis for LHCGR gene was performed. Molecular genetic analysis identified a pathogenic variant of LHCGR (c.1730 C>T, p.Thr577Ileu), which was previously reported in a FMPP patient. His father and paternal grand father also carry the same mutation. Anti-androgen treatment with bicalutamide (25mg/day) and aromatase inhibition with anastrozole (1mg/day) were initiated. After treatment, there was improvement in pubertal progression, accelerated growth velocity and rate of skeletal maturation without any specific side effects. Presentation: Thursday, June 15, 2023