Islet Autoantibodies in the Patients with Sjogren’s Syndrome and Thyroid Disease and Risk of Progression to Latent Autoimmune Diabetes in Adults: A Case Series

The glutamic acid decarboxylase 65 antibody (GAD65-Ab) is an autoimmune marker in some diseases such as diabetes or autoimmune disorders of the central nervous system such as stiff-man syndrome. It can appear with other pancreatic autoantibodies, such as insulin autoantibodies (IAA), presenting as early signs of pancreatic islet β-cells impairing, and play roles in the pathogenesis of type1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA). Positive GAD65-Ab is rarely observed in insulin-dependent diabetic patients with other acquired autoimmune diseases, such as Sjogren's syndrome (SS). Besides, LADA revealed by islet autoantibodies such as GAD65-Ab can also be complicated with Hashimoto's thyroiditis (HT), another autoimmune thyroid disease. To date, whether GAD65-Ab positive in patients with autoimmune diseases predicts the onset or progression to T1D or LADA remains unknown. Herein, two unique cases of middle-aged Chinese Han women free from diabetes for three years are described despite their blood tests persistently testing positive for GAD65-Ab or IAA. Both patients suffered from HT and SS. Follow-up OGTTs (oral glucose tolerance test) for three years revealed that the patients had a well-controlled glycemic level and normal pancreatic function. However, one of the patients had a temporary increase of postprandial glucose after a short-term loss of diet control. The presence of auto-immune antibodies in these patients had little impact on glucose tolerance or insulin secretion in 3 years. The study postulate that both the primary immune injury caused by serum GAD65-Ab positive, an autoimmune marker, and increased body weight contribute to the progression of LADA.