Introduction
ME/CFS disease, orthostatic intolerance, post-exertional malaise
REACTIVE HYPEREMIA, DISEASE, SYNDROME, DILATION, ENDOTHELIAL DYSFUNCTION
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disease with a massive negative impact on quality of life for affected patients [In previous studies, results indicated that a subgroup of ME/CFS patients experienced improvement of symptoms after therapeutic B-lymphocyte depletion using the monoclonal anti-CD20 antibody Rituximab [In order to explore this hypothesis further in a larger study, we conducted a randomized, double-blind placebo-controlled study (RituxME trial) [The clinical presentation of ME/CFS, with major symptoms arising from several organ systems, indicates disturbance of a biological system with widespread functions. Some of the most common and distressing symptoms of ME/CFS, i.e. orthostatic intolerance and post-exertional malaise [One previous study by Newton et al., investigating flow-mediated dilation (FMD) for large vessel endothelial function and post-occlusive reactive hyperemia (PORH) for microvascular function in ME/CFS patients, concluded that ME/CFS patients have both large and small vessel endothelial dysfunction as compared to age- and sex-matched controls [Our hypotheses for the present substudy were 1) FMD and PORH would be reduced in ME/CFS patients, compared to the healthy controls, and 2) There could be a correlation between ME/CFS disease severity and FMD/PORH levels, and lastly 3) If the treatment group showed symptom alleviation, this could be accompanied by an improvement of endothelial function.