Fibromyalgia Screening in Patients With Unexplained Chronic Fatigue

Christopher A. Aakre, MD, MSc


Menopause. 2021;28(1):93-95. 

In This Article

When to Suspect Chronic Fatigue Syndrome or Fibromyalgia

Postexertional malaise—characterized by a prolonged and disproportionate increase in fatigue symptoms after physical, emotional, or cognitive stress—is a feature of fatigue suggestive of either myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or fibromyalgia. Myalgic encephalomyelitis/chronic fatigue syndrome is a poorly understood condition characterized by debilitating fatigue that is otherwise unexplained and minimally relieved by rest, unrefreshing sleep, severe postexertional malaise, orthostatic intolerance, and cognitive impairment (ie, brain fog). Fibromyalgia, on the other hand, is a central sensitization syndrome typified by amplification of pain signals out of proportion to sensory inputs (hyperalgesia) and the generation of pain signals from otherwise innocuous sensory stimuli such as touch (allodynia).[2] Both fibromyalgia and ME/CFS have been associated with postviral syndromes, including coronaviruses.

The diagnostic criteria for fibromyalgia and ME/CFS overlap significantly—up to 70% of patients with fibromyalgia will meet criteria for ME/CFS, whereas 35% to 70% of patients with ME/CFS will meet criteria for fibromyalgia.[3] Despite the symptom and diagnostic criteria overlap, fibromyalgia and ME/CFS represent two distinct clinical syndromes. The peak incidence of ME/CFS is bimodal, during the teen years and the 30 s.[4] The typical age of onset for fibromyalgia is between 20 and 50 years, with increasing prevalence with age. The prevalence is also about two to three times higher in women.[5]

A biologic explanation of the sex differences in the prevalence of fibromyalgia has not been established; however, links between a decline in estrogen and menopause in enhancing chronic pain symptoms have been suggested.[6] Clinical evidence suggests that women may report worsening in their fibromyalgia symptoms around the final menstrual period, or they may report new-onset aches and pains that may meet diagnostic criteria for fibromyalgia. However, limited evidence has not demonstrated improvement in fibromyalgia-associated pain with hormone therapy (HT).[7]

Fibromyalgia is not considered a diagnosis of exclusion, and in fact, it frequently coexists with other conditions associated with myofascial and joint pains.[8] American College of Rheumatology (ACR) fibromyalgia diagnostic criteria in 1990 have evolved from allodynia (pain from a stimulus that typically would not cause pain) at 11 of 18 tender points on examination to a 2016 self-reported survey of widespread pain and severity of related symptoms including fatigue, cognitive symptoms, and sleep quality. Pain generally must be present above and below the waist and on both sides of the body. The pain does not need to be consistently present—the 2016 ACR criteria qualifies pain needing to be present in 1 of 19 body sites within the last week. Because pain in fibromyalgia can be migratory, monitoring specific pain regions may not be necessary unless the site is a primary pain generator undergoing focused treatment. The 2016 ACR criteria's self-reported symptom survey can be adapted to a paper screening tool for general use. Referral to a rheumatologist or general internist can help confirm a suspected diagnosis.

Fibromyalgia onset is often gradual, taking months to years to fully develop, and symptoms can wax and wane in response to physical, emotional, and environmental stressors. Consequently, mean time to fibromyalgia diagnosis from symptom onset has been found to be about 6.4 years.[9] Conversely, patients who develop ME/CFS abruptly fall from high functional levels to severe functional limitations over a short period of time after some "triggering event." Chronic fatigue secondary to fibromyalgia may not have a clearly identifiable triggering event, and as with the characteristic pain symptoms, it comes on more gradually. Pain is not uncommon in ME/CFS, but severe postexertional fatigue is the primary functional limitation of this condition.