BACKGROUND: A sizable part of post-COVID syndrome meets the diagnostic criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). A doubling of cases of ME/CFS within the next years is therefore projected.
OBJECTIVES: Presentation of the current state of knowledge on ME/CFS.
MATERIALS AND METHODS: Unsystematic review of the literature and of own contributions in research and patient care.
RESULTS AND CONCLUSIONS: ME/CFS is a neuroimmunological disease, mostly infection-induced, usually persisting throughout life. Clinically it is characterized by fatigue lasting at least 6 months and the defining core feature of exercise intolerance (post-exertional malaise, PEM). Exercise intolerance is defined as a worsening of symptoms after (even mild) everyday exertion, which usually begins after several hours or on the following day, is still noticeable at least 14 h after exertion, and often lasts for several days (up to weeks or longer). Furthermore, ME/CFS is characterized by pain, disturbances of sleep, thinking and memory, and dysregulation of the circulatory, endocrine, and immune systems. As a separate clinical entity, ME/CFS should be distinguished from chronic fatigue, which occurs as a symptom of a range of very different diseases. The diagnosis of ME/CFS is made clinically using established international diagnostic criteria and requires careful stepwise diagnosis to exclude other diagnoses. A causal therapy for ME/CFS has not been established; the focus is on symptoms relief, treatment of the often accompanying orthostatic intolerance, and assistance with anticipatory energy management (pacing).
