Indirect immunofluorescene assays with patient's serum obtained one year after symptoms onset (dilution 1:10) revealed anti-TPO antibodies specific granular staining in the cytoplasm of the follicle epithelium (A, white arrowheads). Serum of another Hashimoto thyroiditis patient served as positive control showed both granular staining in the cytoplasm of the follicle epithelium (B, white arrowheads) and coarse staining in the colloid of follicles (B, white asterisk), which represented anti-TPO and anti-TG seropositivity, respectively. Phosphate buffered saline solution added as negative control gave neither of the above mentioned fluorescence pattern (C). Positive staining was observed after human embryonic kidney cells transfected with NMDA receptors was incubated with patient's serum (dilution 1:10), confirming the continuing presence of autoantibodies against NMDA receptors (D), while patient's serum didn't react with untransfected human embryonic kidney cells (E). As for the EBV associated serostatus, EBV-VCA-IgG (F), high avidity EBV-VCA-IgG (G) and EBNA-IgG (J) were present in patient's serum, while EBV-VCA-IgM (H) and EBV-EA-IgG (I) were absent, suggesting a chronic EBV infection without relapse or reactivation during follow-up. (Magnifications: 10 × F~J, 20 × A~C and 40 × D~E).