Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia: Definitions, Similarities, and Differences

Abstract

This commentary presents a simplified way of making the diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) using the 1994 Centers for Disease Control and Prevention case definition. The format used can easily be modified for other case definitions. The commentary then discusses whether ME/CFS is the same or a different illness from fibromyalgia. Because overlap exists between the 2 syndromes, some investigators have posited that they are variants of the same illness. I have viewed this as an empirically testable hypothesis and have summoned considerable amounts of data that suggest that the 2 illnesses differ. Were differences to exist, that would suggest different pathophysiologic processes for each, leading to different treatments. (Clin Ther. 2019;41:612e618)

DNA Methylation and Brain‐Derived Neurotrophic Factor Expression Account for Symptoms and Widespread Hyperalgesia in Patients With Chronic Fatigue Syndrome and Comorbid Fibromyalgia

“…One potential limitation of the present study is the inclusion of patients with both CFS and FM. While the degree of overlap between the conditions has been debated and raises important questions about diagnostic criteria and possible shared pathophysiology (61,62), these questions are beyond the aim of the present study. In this study we included patients with CFS and comorbid FM since previous research suggests that comorbidity with FM is arguably the best discriminator between CFS patients with high and those with low symptom burden and disability (4).…”

How Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Progresses: The Natural History of ME/CFS

“…ME/CFS and FM share a number of overlapping core symptoms that mean the two are commonly experienced together; FM has been reported to co-occur in 12–91% of PWME ( 16 , 154 , 155 ). However, there is evidence to suggest the two conditions differ in their hormone dynamics, genetic/molecular biology, and autonomic function ( 156 , 157 ). This is reiterated by the absence of post-exertional malaise in FM ( 158 , 159 ), which is one of the key features of ME/CFS ( 2 , 101 , 102 , 160 ).…”

Numeric Rating Scales Show Prolonged Post-exertional Symptoms After Orthostatic Testing of Adults With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

“…Applying the new systemic exertion intolerance disease (SEID) criteria, in which pain is not included as a cardinal symptom, Jason et al find that SEID patients with FM were more severely disabled than patients without FM ( 47 ). These issues are discussed in more detail in a recent review by Natelson et al ( 48 ). Summarizing, the abovementioned data suggest that there may be a different underlying pathophysiology, but further studies are needed to clarify the true nature of the differences.…”