Persistent Symptoms After Lyme Disease: Clinical Characteristics, Predictors, and Classification.

Persistent symptoms after an infection have been described for a number of infectious diseases, including Lyme disease. Studies have confirmed a moderate but consistent increase in the prevalence of such symptoms after Lyme disease, though the risk increase varies dependent on study design and the definition of persistent symptoms. Various possible predictors have been proposed, including a dysregulation of the immune system, metabolic changes, increased sensitization to pain signals, cognitive-behavioral factors, or-controversially-the persistence of the causative Borrelia bacteria or remnants thereof. Research on the precise roles of any of these factors is still ongoing. The lack of biological underpinning also makes it difficult to assess with certainty which patients' (generally nonspecific) persistent symptoms are etiologically related to the previous Lyme disease episode and which are not, particularly as these symptoms occur in the general population relatively frequently. The diagnostic criteria for posttreatment Lyme disease syndrome have shown their usefulness in both clinical and research settings but leave out a number of patients whose symptoms may fall just outside said criteria. Though the relationship between these symptoms and the previous Lyme disease episode may be very uncertain, we would argue that a uniform description and classification of these patients will aid in future research and patient management, regardless of the eventual underlying cause. Thus, we argue for an inclusive classification system for all persistent symptoms attributed to Lyme disease in order to promote validation of patient experiences and perspectives, while also maintaining scientific nuance regarding the very uncertain etiology of these patients' symptoms.