Hippocampal Function and Markers of Citrullinated Proteins and Bacterial and Viral Infection in Fibromyalgia

INTRODUCTION: Fibromyalgia is associated with dyscognition or "fibro fog", of unknown aetiology. The hippocampus has major roles in memory and cognition. Certain bacterial and viral infections can cause hippocampal changes. Furthermore, citrullinated proteins may accumulate in the hippocampus in Alzheimer's disease. OBJECTIVES: This study aimed to test the hypothesis that hippocampal functioning in fibromyalgia is associated with markers of bacterial and viral infection and serum anti-cyclic citrullinated peptide antibody (anti-CCP) levels. METHODS: Hippocampal functioning was assessed in 26 female patients and one male patient with the Paired Associates Learning Total Errors (Adjusted) (PALTEA) in a cross-sectional study. Serum samples, for markers of bacterial and viral infections and anti-CCP, were taken within an hour of cognitive assessment. RESULTS: Generalised linear modelling (p = 0.01) with PALTEA as the dependent variable showed significant coefficients for Borrelia outer surface protein peptide mix (p = 0.025), lymphocyte function-associated antigen-1 (p = 0.003), Ehrlichia chaffeensis plus Anaplasma phagocytophilum (p = 0.048), Mycoplasma pneumoniae immunoglobulin (Ig) G (p = 0.003), coxsackievirus B1 IgA (p = 0.010), echovirus IgG (p = 0.012), and anti-CCP IgG (p = 0.003). CONCLUSION: On the basis of this study, it is suggested that, in fibromyalgia patients complaining of dyscognition, there may be merit in assessing lymphocyte function-associated antigen-1, anti- CCP IgG, and evidence of infection with Borrelia species, Ehrlichia chaffeensis, Anaplasma phagocytophilum, Mycoplasma pneumoniae, coxsackievirus B1, and echovirus.