Background: Type 1 diabetes (T1D), the most frequent type of diabetes in paediatrics, can be easily misdiagnosed presenting with hyperglycaemia due to monogenic diabetes. Objective and hypotheses: We report a 13-year-old boy with monogenic diabetes, initially diagnosed and treated as T1D.
Method: The patient presented at 7.5 years of age with a febrile illness and mild hyperglycaemia. An oral glucose tolerance test (OGTT) then was normal, HbA1c 6.3% (45 mmol/mol). Slowly progressing T1D was diagnosed; he stayed under follow-up with routine BMstix measuring at home (max blood glucose (BG) 153 mg/dl (8.5 mmol/l). A repeat OGTT at the age of 9 years showed BG 127 mg/dl (7.1 mmol/l) at 0 and 258 mg/dl (14.3 mmol/l) at 120, HbA1c 6.7% (50 mmol/mol). He started on small doses of insulin. His glycaemic control was excellent; he remained on small doses of insulin (0.1 U/Kg/d) for 4 years. The patient discontinued insulin without medical advice. Six months later, he had mild fasting hyperglycaemia, (BG 107148 mg/dl (68 mmol/l)), HbA1c 6.2% (44 mmol/mol); Anti-GAD, ICA and IA2 were negative. OGTTs were normal for father and younger sister aged 2 years. His mother, 37 year old, had gestational diabetes, her OGTT showed BG 147 mg/dl (8.2 mmol/l) at 0 and 121 mg/dl (6.7 mmol/l) at 120, HbA1c 6.4% (46 mmol/l); negative anti-IA2 antibodies. DNA analysis was carried out for the presence of mutations in HNF1A and GCK genes employing bidirectional sequencing of the coding regions of the two genes. MLPA was employed to search for deletions in the genes GCK, HNF1A, HNF4A, HNF1B.
Results: Point mutations were not detected in the genes GCK and HNF1A. The MLPA revealed that the patient and his mother were heterozygotes for GCK gene deletion (exons 110).
Conclusion: MODY2 is a form of monogenic diabetes resulting in β-cell dysfunction, characterized by mildly elevated fasting blood sugars and HbA1c ranging from 5.67.6% (3860 mmol/mol). It is frequently unrecognized or misdiagnosed as T1D or T2D, resulting in unnecessary insulin treatment.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology