OBJECTIVE: The authors’ goal was to determine whether D8/17, a rheumatic fever susceptibility trait marker, identifies a possible type of anorexia nervosa: pediatric autoimmune neuropsychiatric disorders associated with streptococcus (PANDAS) anorexia nervosa. METHOD: Using immunofluorescence, the authors measured the percentage of D8/17-positive B lymphocytes in the peripheral blood of 16 subjects 7–21 years old who had not had rheumatic fever but who had possible PANDAS anorexia nervosa. The comparison subjects were 17 psychiatric patients with no eating disorder and no PANDAS characteristics. Subjects were considered D8/17 positive if they had 12% or more D8/17+ cells. RESULTS: There were more D8/17-positive individuals among those with PANDAS anorexia nervosa (81%) than among the comparison subjects (12%). The subjects with PANDAS anorexia nervosa had a higher percentage of D8/17+ cells (mean=27.1%, SD=17%) than the comparison subjects (mean=5.3%, SD=7.4%). CONCLUSIONS: A larger study is needed to determine whether D8/17 serves as a marker for susceptibility to a type of anorexia nervosa.