MON-123 Atypical Diabetes Mellitus or Type 1 Diabetes Mellitus?

Abstract

Introduction: Autoimmune (AI) polyglandular syndromes (APS) share common susceptibility gene variants and therefore have strong genetic predisposition. Type 1 APS includes chronic mucocutaneous candidiasis, hypoparathyroidism and adrenal insufficiency. Type 2 APS includes adrenal insufficiency and at least one of following: AI thyroiditis or type 1 diabetes (T1DM). Type 3 APS variant is AI thyroiditis and T1DM without adrenal insufficiency. Furthermore, no single diagnostic test can consistently distinguish T1DM from type 2 diabetes (T2DM). In clinical practice it is important to recognize APS, so that the correct diagnosis can be made. Case: A 44 year old African American female with AI hypothyroidism, and orthostatic hypotension presented with the complaint of blurry vision. She had a strong family history of DM and was concerned about developing diabetes herself. [(BMI= 30.3 kg/m²), (Fasting blood glucose (BG) =111 mg/dL), (Hba1c level of 6.3%), (glutamic acid decarboxylase (GAD-65) antibodies >30; normal=0-1.01 U/mL), (C-peptide= 1.28; normal = 0.81-3.85 ng/mL)]. Continuous glucose monitor testing showed normal pre-prandial levels with post-prandial elevated BG to 178 mg/dL. Due to elevated BG, elevated GAD-65, and family history of DM, a diagnosis of T1 DM was made. She was started with low dose insulin (detemir 1 units daily), and increased slowly to 6 unit daily. During this time, Hba1c ranged from 6-6.4%. Over the next few years, she made drastic lifestyle changes (strict diet and increased physical activity). She then developed an eating disorder and lost 86 lbs. (BMI=17.5 kg/m²). She started to have hypoglycemic episodes (HYPO), more so from exercise. The insulin dose was decreased to 2 units daily on days of no exercise, due to HYPO. Hba1c dropped to 5.2%. She continued to have recurrent HYPO (BG in 40’s with Hba1c= 4.3%). Therefore, insulin therapy was discontinued. She has not taken exogenous insulin for the past three years (most recent Hba1c=6.6%). GAD-65 continues to be elevated (>250 U/mL) and she continues to have a normal C-peptide level of 2.67ng/mL. She no longer has HYPO. Discussion: The clinical case presented describes atypical DM that depicts slowly progressive autoimmune diabetes. The patient had phenotypical features that could be suggestive of T2DM with insulin resistance - obese at initial presentation, ethnicity, family history of DM, post-prandial hyperglycemia, and not requiring insulin for many years. However, it is important to assess all the patient’s clinical conditions and consider possibility of APS. It is also important not to assume a patient has T2DM and consider atypical diabetes in a patient with features suggestive of APS. Studies have shown that up to 30% of individuals with the classical appearance and presentation of T2DM have positive autoantibodies, and may have slowly progressive type of autoimmune diabetes.