Two cases of type 2 diabetes revealed transient positive for anti-GAD antibodies following treatment with immunoglobulin

Anti-glutamic acid decarboxylase (anti-GAD) antibodies were detected in two diabetic patients after they underwent treatment with intravenous immunoglobulin (IVIg). Case 1: A 76-year-old man was given IVIg to treat chronic inflammatory demyelinating polyneuropathy (CIDP), and 11 days later, his anti-GAD antibody level was 32.4 U/mL. However, 471 days later, the level dropped to negative values. Following the second IVIg treatment, his anti-GAD antibody level increased to 11.4 U/mL after 11 days but became negative again 36 days later. Case 2: A 33-year-old man was given IVIg to treat Guillain-Barré syndrome, and his anti-GAD level was 32.4 U/mL on the third day following IVIg. However, 21 days later, the level had decreased to 8.5 U/mL. He was given IVIg again, but after 127 days, the level once more became negative. The anti-GAD antibody levels were measured using a commercial enzyme-linked immunosorbent assay. Our results indicate that the transient appearance of anti-GAD antibody was associated with IVIg. Therefore, we suggest that confirming whether patients were given IVIg prior to the classification of their diabetes is essential in clinical practice.