What is M.E.?
Although the aetiology of M.E. is unknown, emerging evidence about the cause of M.E. includes autoimmune deficiencies, viral infections, autonomic nervous system dysfunction and genetic factors, among others. Evidence suggests a population prevalence of at least 0.2–0.4% which means that a general practice with 10,000 patients is likely to have up to 40 patients with M.E.1 They might be difficult to identify from their prescriptions because there is no specific treatment that is licensed for M.E. At present, there is only symptom management available, so you might see chronic pain, sleep, migraine, nausea, dizziness or depression treatments, among others, on prescriptions. M.E. patients often have multimorbidity2 so even if they are not taking prescribed medication for their M.E. symptoms, you may still come across them. It is important to know how M.E. may affect the safe and effective use of medicines and the services you provide. As a long-term, fluctuating condition, M.E. is categorised as a disability by the Equality Act 2010.3
Symptoms
There are many symptoms of M.E. affecting many body systems, listed in the Symptoms and management quick reference table on p 12. Not all patients will experience all of these symptoms all of the time. Any new symptoms should always be checked, even if they may seem related to M.E. (see Red flags for referral on p 6.) For recent research findings relating to the multi-system nature of the illness and its symptoms, please see the Pathophysiology quick reference table on p 11. Symptoms can fluctuate and women with M.E. often find that symptoms worsen at different times in their menstrual cycle. If a patient appears better or worse at a given moment, this does not indicate a change in their overall condition. The characteristic symptom of M.E. which differentiates the illness from fatigue experienced in other conditions is post-exertional malaise, sometimes referred to as “payback.”4 This is defined as the body’s inability to recover after expending even small amounts of energy on simple physical or mental activity.1 The onset of post-exertional malaise is delayed for at least 24 hours, with slow recovery over several days. Some patients also experience widespread muscle and neuropathic pain, along with worsening of their other symptoms, as part of post-exertional malaise. The fatigue experienced by people with M.E. is very different from ordinary tiredness or sleepiness. Simple physical and mental activities can leave patients struggling to function, and pushing through this can trigger post-exertional malaise. For this reason, the National Institute of Health and Care Excellence’s guideline for M.E. (NICE CG53, see p 6) stresses that M.E. patients need to space out their activities and may find that their capacity is typically greater at a specific time of day.
Severity and function levels NICE CG53 describes three levels of severity of M.E.:1 • People with mild M.E. are mobile, can care for themselves and can do light domestic tasks but with difficulty. Most are still working or in education, but to do this they have probably stopped all leisure and social pursuits. • People with moderate M.E. have reduced mobility and are restricted in all activities of daily living, although they may have peaks and troughs in their level of symptoms and ability to do activities some of the time. • People with severe M.E. are unable to do any activity for themselves, or can only carry out minimal daily tasks (such as face washing, cleaning teeth). They have severe cognitive difficulties and depend on a wheelchair for mobility. Complications can develop in severe M.E. as a result of being mostly bedbound, such as postural hypotension, deep venous thrombosis, osteoporosis, pressure sores and deconditioning.1
