Fatigue in ANCA-associated vasculitis (AAV) and systemic sclerosis (SSc): similarities with Myalgic encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).  A critical review of the literature.INTRODUCTION
 Persistent debilitating fatigue is a frequent complaint in patients with systemic autoimmune rheumatic diseases (SARDs).  Fatigue is, however, frequently overlooked in the clinic, and patients who successfully achieve remission of their disease, often still have a lowered quality of life due to its persistence.  How similar is this fatigue to Myalgic encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), what is this fatigue associated with, and what tools/approaches (if any), have resulted in the improvement of fatigue in these patients is poorly defined.


 AREAS COVERED
 Similarities between the pathophysiology of ME/CFS, systemic sclerosis (SSc) and primary systemic vasculitides (PSV) are discussed, followed by an in-depth review of the prevalence and correlates of fatigue in these diseases.  The authors reviewed literature from MEDLINE, APA PsycInfo, Embase, and CINAHL.


 Persistent fatigue is a prominent feature in SARDs and may not be associated with components commonly associated with disease activity and/or progression.  Immune and metabolic commonalities exist between ME/CFS, SSc, and PSVs - suggesting that common pathways inherent to the diseases and fatigue may be present.  We suggest that patients with features of ME/CFS need to be identified by treating physicians, as they may require alternative approaches to therapy to improve their quality of life.
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