Abstract: Objective: To explore the clinical features of 48, XXYY syndrome with diabetic; to analyze parental origin of X-chromosome and skewed X-inactivation. Methods: The clinical data were collected; Genomic DNA was extracted from a whole blood sample. The parental origin of X chromosome and skewed X-inactivation were analyzed using PCR combined Hpa Ⅱ restriction enzyme digestion. Results: The patient was diagnosed as 48, XXYY syndrome with diabetes according to the clinical presentations and laboratory examinations. Plasma glucose level remained stable after metformin plus testosterone treatment. The X chromosome were inherited from the patient’ father and mother. The degree of skew of X-inactivation was 0.52. Conclusion: The pathogenesis of diabetes in 48,XXYY patient may be associated with low testosterone levels and insulin resistance. The extra X chromosome of our case and other had reported eight cases of 48, XXYY syndrome were paternal origin. Not all of 48,XXYY syndrome patients had skew X-inactivation.

Key words: 48, XXYY syndrome, Diabetes, Skewed X chromosome inactivation