Characterizing Sjögren-Associated Fatigue: A Distinct Phenotype from ME/CFS

Abstract

Fatigue is the most commonly reported and debilitating extraglandular symptom of primary Sjögren's syndrome (pSS). Fatigue and exertional intolerance are hallmark  symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We aimed  to characterize fatigue and further symptoms among pSS patients and to determine  whether there is a symptom overlap in pSS and ME/CFS. In 19 patients with pSS, we  assessed pSS symptom severity and disease activity via questionnaires as well as  the Canadian Consensus Criteria (CCC) for ME/CFS. Hand grip strength (HGS) and  levels of α1-, α2-, β1-, β2-, M3- and M4-receptor-autoantibodies were measured. A  subgroup of pSS patients exhibited severe fatigue and had higher severity of pain  (p = 0.045), depression (p = 0.021) and sleep disturbances (p = 0.020) compared  to those with less fatigue. Four of eighteen pSS patients fulfilled the CCC. HGS  parameters strongly correlated with fatigue severity (p < 0.05), but strength  fully recovered one hour after exertion in contrast to ME/CFS. Levels of β1-, β2-  and M4-receptor-autoantibodies were elevated and correlated significantly with  disease activity assessed by the ESSDAI (p < 0.05), but not fatigue severity.  Only a minor subgroup of pSS patients fulfills the CCC, and post exertional  malaise (PEM) is atypical, as it is primarily triggered by mental/emotional but  not physical exertion. HGS assessment is an objective measure to assess overall  fatigue severity.