·The clinical manifestations, the level of sex hormones, and the gonads pathology of the patients with 45,X/46,XY mosaicism diagnosed by G-banding karyotype analysis and fluorescence in situ hybridization (FISH) were retrospectively analyzed, who were admitted in Children's Hospital of Soochow University from January 2014 to December 2020.

·Twenty-three patients with 45,X/46,XY mosaicism were included, among whom 11 cases were the female phenotype, and 12 cases were the male phenotype. In these patients, 12 patients were diagnosed by G-banding karyotype analysis, 10 patients were diagnosed by FISH, and only 1 patient was diagnosed by array-based comparative genomic hybridization. The age of the first diagnosis was 0.3?14.9 years. The mean age of the patients with the female phenotype was (9.3±3.9) years, which was bigger than that of the male phenotype [(4.4±3.7) years, P<0.05]. All the patients above 1 year old had different degrees of short stature, especially in the female phenotype patients. In the female phenotype patients, three patients had clitoromegaly, while the other patients had no masculine appearance of external genitalia. The external masculinisation scores (EMS) of the patients with the female phenotype were 0?2.5. Twelve patients with the male phenotype were in pre-adolescent state, among whom 4 patients had hypospadias combined with cryptorchidism, 3 patients had hypospadias, 3 patients had small testicles, and 2 patients had normal external genitalia. The EMS of them ranged from 4 to 12, with a mean score of 10.5. All the patients with the female phenotype had hypergonadotropic hypogonadism, while most of the patients with the male phenotype had gonadotropin levels matched with their age. There were 3 patients with the female phenotype having gonadoblastomas.

·The 45,X/46,XY mosaicism patients present a wide spectrum of manifestations. The risk of gonadal malignancy onset should be emphasized. EMS has guiding significance for clinical evaluation of these patients.