SUN-LB035 Blood Glucose Trends Documented by Continuous Glucose Monitors Can Be Foundational in the Diagnostic Evaluation of MODY 2

Background MODY 2 is a genetic mutation in the glucokinase (GCK) gene characterized by elevated fasting blood glucose which improves with meals. Pancreatic GCK regulates insulin secretion and mutations in the GCK gene alter the insulin secretion pattern. Although blood glucose averages are higher in people with MODY 2 that those without diabetes, there are no reported increases in morbidities or mortalities excepting a predilection for gestational diabetes in women. Therefore, identification of MODY 2 is helpful in minimizing cost, blood work, and medication exposure in affected patients. Clinical Case Two brothers, ages 13 and 15 years, have had hyperglycemia of unclear origin for 3 years. Initial evaluation of hyperglycemia was the result of screening triggered by paternal history of hyperglycemia and abnormal HbA1c. In the initial evaluation, the 13-year-old had a fasting blood glucose of 103 mg/dL and HbA1c of 6.2% and the 16-year-old had a fasting blood glucose of 100 mg/dL and HbA1c of 6.3%. Both brothers were born at term between 40-42 weeks gestation with birth weights that were appropriate for gestational age. Their mother did not have gestational diabetes during either pregnancy. They are clinically asymptomatic and deny polyuria, polydipsia, nocturia, enuresis, or weight loss. Neither brother had acanthosis nigricans on exam nor an abnormal BMI for value for age (z=-0.67). There is a family history of diabetes and hyperglycemia on the paternal side. Father was diagnosed with hyperglycemia for several years with fasting hyperglycemia and a HbA1c range of 6.3-6.7%. He was eventually started on metformin despite stable HbA1c trend and being clinically asymptomatic. Given the high suspicion for MODY 2 for the brothers and difficulty in evaluating genetics due to insurance coverage limitations, one brother was started on continuous glucose monitor (CGM) to determine if his glycemic trend as expected in MODY 2. The CGM trends demonstrated fasting hyperglycemia with improvement of blood glucose throughout the day and post prandially. With documented glycemic patterns typical for MODY 2, insurance approved genetic testing. Both brothers tested positive for the same mutation, heterozygous mutation in the GCK gene, c.802G>A (pGlu268Lys), a mutation typical in MODY 2. The father was subsequently tested and also tested positive for the same mutation in the GCK gene. With the diagnosis of MODY 2, the brothers continue routine care with their pediatrician with yearly laboratory studies and their father was able to discontinue metformin. Conclusion In patients with a strong family history of hyperglycemia but HbA1c consistently below 7%, MODY 2 should be considered. Using continuous glucose monitors to identify classic MODY 2 glucose patterns can be helpful in diagnosing this benign condition when genetic testing is unavailable, thereby significantly impacting patients and their families. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.