Child: male, 3 years old, admitted with the main reason of “penile enlargement for more than 2 years”. More than 2 years before admission, his parents noticed that the child’s penis was longer than that of the surrounding infants (specific data not available). The child had a dark scrotum and a dark but uniform skin tone all over his body. Six months ago, the parents found that the child’s external genitalia were developing significantly faster, and the change of voice was not obvious. Before admission, cortisol 67 ng/ml, ACTH 23.5 pg/ml, estradiol 20 pg/ml, testosterone 4.28 ng/ml, progesterone 0.46 ng/ml, luteinizing hormone 1.0 mIU/ml, follicle stimulating hormone 1.1 mIU/ml were found in the local hospital. She had no history of recurrent vomiting or diarrhea, no involuntary laughter, and rapid height growth over the past 6 months. Personal and family history: full-term normal delivery, second birth, birth weight 2750g. She was healthy in the neonatal period and had no obvious feeding difficulties. The child’s sister was physically fit. The child’s cousin had congenital adrenocortical hyperplasia of simple masculine type and underwent vulvoplasty in our hospital 3 years ago. Physical examination: height 99.5 cm, weight 15.8 kg, blood pressure 100/70 mmHg, normal nutritional development, dark, uniform skin color, good skin elasticity, low subcutaneous fat, moist oral mucosa, no pigmentation, no obvious whiskers on the lips, penis length 7 cm, circumference 7 cm, bilateral testicular volume 12 ml, pubic hair Tanner stage II, dark scrotum color. Auxiliary examinations: cortisol: 7.8ug/dl, ACTH: 27.7 pg/ml; blood gas examination was normal; electrolyte examination was normal; chorionic gonadotropin 1.21 m IU/ml, normal; methemoglobin: 1.3ng/ml; sex hormones:, testosterone 246 ng/dl, luteinizing hormone 1.7 mIU/ml, testosterone and luteinizing hormone were elevated, follicle Stimulating hormone, estradiol, and progesterone were normal; bone age: equivalent to 3 years; adrenal ultrasound and CT: no adrenal enlargement, no occupancy in the adrenal region; testicular ultrasound: testicular volume increased, homogeneous echogenicity; pituitary MRI: isosignal occupancy at the level of gray nodules, no enhancement after enhancement, long T2 signal seen in the pituitary gland, no enhancement after enhancement, clinical impression: gray nodular misshapen tumor, rathke cyst. Treatment history: After admission to the hospital to improve the examination and clarify the diagnosis, the patient was discharged after being referred to neurosurgery for surgical treatment. (2) The main manifestations were early development of secondary sexual characteristics, including thickening and enlargement of the penis and increased testicular development, with accelerated growth over the past six months; (3) elevated androgen levels; (4) normal cortisol and ACTH levels; (5) no abnormalities in adrenal imaging; (6) MRI of the pituitary gland suggested (6) MRI of the pituitary gland revealed a gray nodular misshapen tumor and rathke’s cyst. Precocious puberty can be diagnosed based on the development of secondary sexual characteristics and accelerated growth before the age of 9 years. Precocious puberty is classified into central and peripheral precocious puberty according to the presence or absence of initiation of the hypothalamic-pituitary-gonadal axis (HPGA), which can also be referred to as true precocious puberty and pseudoprecocious puberty. Because of the presence of testicular development in this child, central precocious puberty should be diagnosed. The etiology of central precocious puberty in males mainly includes the following aspects: ① central nervous system tumors: including malformation tumors, ventricular meningioma, pineal tumors, gliomas, etc.; ② central nervous system infections; ③ congenital developmental abnormalities of the central nervous system: including having hydrocephalus, abnormal development of the optic septum, arachnoid cyst, brain atrophy, brain injury, etc.; ④ secondary to diseases that cause masculinization: such as congenital adrenocortical hyperplasia (CAH), adrenal and testicular mesenchymal hormone-secreting tumors can have pseudoprematurity developing into true precocious puberty; ⑤ HCG-secreting tumors within or outside the central nervous system (liver, testes, retroperitoneum); ⑥ Sporadic or familial male precocious puberty: mainly due to mutations in the luteinizing hormone receptor (LHR) gene; ⑦ Other causes include: intracranial radiotherapy chemotherapy, Fetal alcohol syndrome, chromosomal abnormalities, Williams syndrome, hypothyroidism; ⑧ Idiopathic precocious puberty: children with precocious puberty for which no exact cause is found are diagnosed as idiopathic precocious puberty. This child has two prominent features: a boy with early onset. Male precocious puberty usually occurs between preschool and 9 years of age, and this child was just 3 years old. Therefore, the main differential diagnosis for this child included sporadic male precocious puberty due to LHR gene mutation, central nervous system tumor, testicular tumor, and idiopathic precocious puberty. The child had no clear history of CNS infection, cephalofacial dysplasia, no history of radiotherapy, etc. The biochemical examination and adrenal cortical function were normal, so congenital developmental abnormalities, CNS infection, and central precocious puberty due to CAH could be excluded. Ultrasound examination of the adrenal glands of the testes could exclude testicular occupational lesions. The diagnosis was clear after the MRI examination after admission, and hypothalamic malformation tumor was the cause of central precocious puberty in the child’s male.