ABSTRACT
We report a case of a female teenage with monogenic diabetes mellitus caused by glucokinase regulator (GCKR) gene mutation who presented with diabetic ketosis and misdiagnosed as type 1 diabetes. The patient was treated with insulin for 3 years since diagnosis. The islet function was well preserved, but polycystic ovary syndrome was developed. Whole-exome gene sequencing revealed a GCKR gene c. 69delG heterozygous mutation. After molecular diagnosis, the insulin dosage was gradually reduced to full cessation, and only metformin sustained-release tablets were taken to control blood glucose. It is necessary to regular evaluate islet function of patient with type 1 diabetes, and genetic test is of significance for accurate diagnosis and treatment.