Myalgic Encephalomyelitis (ME), formerly known as chronic fatigue syndrome (CFS) and often still referred to as ME/CFS, is a devastating, chronic, complex, multi-system illness. ME occurs in children, adolescents and adults of all ages and backgrounds.
There is clear recognition that ME is a serious disabling disease rooted in dysfunctions that impair energy production, the immune system, the nervous system and more.
The onset of ME is often sudden, but it can also develop gradually, typically following a viral or other type of infection. The SARS-CoV-2 virus (known as COVID-19) is the most recent example of this happening, with as many as 30% of acute COVID cases developing into Long COVID or PASC (post-acute sequelae of COVID-19), and 50% or more of those developing into ME.
The cardinal symptom of ME is post-exertional malaise (PEM) or post-exertional symptom exacerbation (PESE), which is the worsening of symptoms after physical or cognitive exertion and usually presenting ~24-72 hours after the triggering event. Patients often describe PEM as a ‘crash’ that may take days, weeks, months or longer to recover from.
Core symptoms include profound and debilitating fatigue, unrefreshing sleep, cognitive impairment, orthostatic intolerance, autonomic impairment, chronic and severe ‘flu-like’ symptoms such as tender or swollen lymph nodes, fever, headache, sore throat, as well as chronic pain, gastrointestinal symptoms and sensitivity to sound and light.
While any illness can co-exist with ME, there are several common comorbidities to be aware of. These include Fibromyalgia, POTS, dysautonomia, MCAS, EDS or hEDS, small-fibre neuropathy, SIBO, gastroparesis and IBS.
People with ME find it difficult (or impossible) to function as they did prior to illness onset, including with activities of daily living (e.g., showering, making meals). ME can present with a wide range of severity and up to 25% are bedbound or housebound at some point in their illness (many indefinitely) and 75% are unable to work.
Diagnosis is made using one of several accepted criteria. In line with the US National Institutes of Health recommendations and international best practice, the ICanCME Research Network uses the Canadian Consensus Criteria (CCC) and the IOM (now Academy of Medicine) definitions.