Abstract

Coexistence of Type 1 diabetes mellitus (T1DM) with glucokinase maturity-onset diabetes of the young (GCK-MODY) is extremely rare. Herein, we reported a case, conducted a systematic review and summarized the other reported cases to enhance the awareness of this rare diabetes subtype. An 11-year-old boy was presented with polydipsia, polyuria, and weight loss. He was diagnosed with T1DM based on significant hyperglycemia, decreased C-peptide levels, and positive diabetes-related antibodies. Genetic testing revealed that both the patient and his father carried a heterozygous mutation in the GCK gene. Due to the coexistence of GCK-MODY, the patient experienced difficulties in glycemic control and frequent hypoglycemia during insulin therapy. The patient's father gradually reduced and discontinued insulin treatment after genetic test. In clinical practice, the possibility of overlapping diabetes types should be highly emphasized. Genetic testing should be performed to optimize treatment plans and improve patient outcomes.