When Type 2 Diabetes Isn’t Type 2: Latent Autoimmune Diabetes in a Lean, Highly Physically Active Adult

Latent autoimmune diabetes in adults (LADA) is frequently misclassified as type 2 diabetes mellitus (T2DM), leading to delayed diagnosis and suboptimal management. We report a lean, highly physically active adult engaged in sustained, high-intensity physical activity as part of his occupation, in his early 70s, with a 30-year history of presumed T2DM who was referred for endocrine evaluation because of persistent glycemic instability despite insulin therapy. He reported frequent symptomatic episodes of both hyperglycemia and hypoglycemia, resulting in significant occupational stress, as maintenance of physical fitness and body weight was essential for continued employment. Hemoglobin A1c (HbA1c) values remained persistently elevated, ranging from 7.8% to 9.6% (reference range: 3.8%-5.6%), with marked glycemic variability and failure to achieve stable control. Given his low body mass index (BMI) of 20 kg/m² (reference range: 18.5-24.9 kg/m²) and pronounced glucose fluctuations, evaluation for autoimmune diabetes was pursued. Laboratory testing demonstrated markedly elevated glutamic acid decarboxylase (GAD65) antibodies (204 IU/mL; reference range