"Chronic Epstein-Barr virus infection" syndrome and polymyalgia rheumatica.
Buchwald, D, Sullivan, J L, Leddy, S et al.·The Journal of rheumatology·1988
This study looked at 23 patients with polymyalgia rheumatica (PMR), a condition causing muscle pain and stiffness, and noticed many also experienced severe fatigue, sleep problems, and recurring sore throats—symptoms similar to ME/CFS. Even after treatment improved their muscle pain, these fatigue-related symptoms continued for months. However, blood tests showed their Epstein-Barr virus antibody levels were normal and similar to healthy people their age, suggesting the virus wasn't the primary cause.