I. Jon Russell
The central neurologic soft tissue pain condition, called fibromyalgia syndrome (FMS), and the autoimmune peripheral nerve injury condition, called chronic inflammatory demyelinating polyneuropathy (CIDP), are both potentially disabling. Either condition can accompany an arthritis condition. The general population prevalence of FMS is about two percent, while CIDP is less common, at less than one percent. On this basis, overlap (being comorbid) of FMS and CIDP by chance would be expected in about two per ten thousand of the general population or in about one percent of persons with FMS. By contrast, these conditions are reported to be comorbid (i.e., FMS/ CIDP overlap) in thirty percent of FMS. This high level of association between FMS and CIDP has not yet been adequately explained. Fortunately, validated diagnostic criteria are available for both conditions so they can be distinguished from each other on the bases of established clinical criteria. A self-report questionnaire, based on the 2010 American College of Rheumatology Fibromyalgia Diagnostic Criteria can be used as support for the clinician's diagnosis of FMS (sensitivity ninety six percent). CIDP can be diagnosed using the electrophysiology-based European Federation of Neurological Societies/Peripheral Nerve Society criteria (sensitivity ninety six percent). Neurologic consultation is key to the diagnosis of CIDP. Lower extremity weakness and/or hyporeflexia in a patient with FMS should prompt consideration of FMS/CIDP. Many or all of the chronic manifestations of FMS/CIDP can improve with a course of intravenous immunoglobulin. There are potential risks associated with intravenous immunoglobulin therapy, but clinicians and patients will often conclude that the severity of the impairment associated with FMS/CIDP justifies some therapeutic risk. The threshold for treatment of FMS/CIDP should be low because the potential for benefit is high.