Abstract:Abstract: Objective: To investigate the clinical phenotype and genetic characteristics of a patient with ring chromosome 12. Methods: The symptoms, signs and imaging data of one patient with ring chromosome 12 were collected. The genetic characteristics of ring chromosome 12 were determined by the chromosome G banding technique, chromosomal microarray analysis (CMA), fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) assay. Results: The patient with ring chromosome 12 had twice spontaneous abortions, and the other clinical signs were normal. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), testosterone (T), progesterone (P) and prolactin (PRL) levels were normal, but serum anti-Mullerian hormone (AMH) level (0.57 ng/mL) was lower than the reference interval. There was no abnormal abdominal B-mode ultrasonography. The karyotype of the patient was mos 46, XX, r (12) (p13q24) [96] / 45, XX, and 12 [3] / 46, XX, dic r(12;12) (p13q24) [1]. The CMA results showed that there was the deletion of small fragments in the region of 12q24.33, and that the deletion region belonged to benign copy number variants (CNVs). The FISH results showed that there was deletion in the end of long arm of ring chromosome 12. The MLPA results showed that there was the deletion of subtelomere in the end of long arm of chromosome 12. Conclusion: The patient with ring chromosome 12 has normal clinical signs, and her clinical manifestations are related to the proportion of mosaic karyotype and the number of deletion in the end of long arm of chromosome 12. The abortion of the patient may be associated with the instability of ring chromosome 12.