As clear as MUD

Somewhat contrary to popular perception, it is both very and increasingly common for people to have medically unexplainable symptoms; this is also referred to as ‘medically unexplained disease’ or MUD. The basis of MUD is ‘symptoms’ that cannot be fully explained by an ‘organic’ cause. Managing patients with such a condition is a challenge for physicians, as most people present with a high level of concern and worry about their symptoms and are difficult to reassure. Perhaps the most important role for physicians is to restrict the likelihood of harm caused by unnecessary investigations and treatment. The subject of MUD is controversial and has been so both before and after a chronically fatigued Florence Nightingale took to her bed; the prevalence, outcome and cost of MUD is now such that it ‘deserves’ editorial attention. Treating doctors often feel frustrated and inadequate, and sufferers frequently think they have been rejected; many receive little or no support, or meaningful care on the one hand, or ‘consume’ considerable and usually unhelpful healthcare on the other. There are several reasons for this controversy. First, MUD is frustratingly common and increasingly so. In a range of primary care settings: • Complaints of chest pain, fatigue, dizziness, headache, swelling, back pain, shortness of breath, insomnia, abdominal pain and numbness were responsible for as much as 40% of all visits, but only 26% were ever ‘medically explained’; • More than 25% of all patients in studied English general practices had symptoms that were not medically explicable; • Between 25% and 50% of patients had unexplainable symptoms in various cohorts, which made this problem the most common category of complaint in primary care patients; • Medical explanations were found over a 3-year period in a North American general practice for only about 10% of those presenting with chest pain and headache, and in less than half of those whose primary initial complaint was fatigue, dizziness, oedema, numbness, back pain, dyspnoea, abdominal pain and insomnia, and in another similar study, more than half of patients presenting with a physical symptom had ‘resolved’ by 5 years while a third remain medically unexplained. This level of MUD is also true but less well studied in developing communities. Predictably, given that a common reason for a referral from a primary to a secondary care physician is the former not being able to identify a medical explanation for a patient’s symptoms, the rate of persistence is even greater in secondary care settings – the symptoms of 25% of patients with MUD managed by primary healthcare providers persisted for more than a year compared with 50% in secondary care. Second, the label of medically unexplained symptoms or disease is itself part of the problem. It is an unhelpful term for patients at a time when they are often seeking an explanation for their symptoms, as it promotes a mode of thinking about the issue that regards symptoms as either being ‘organic’ or ‘psychological’, and perhaps most importantly, the term characterises the patient’s complaints by what they are not rather than what they are. This frustration has led the working group revising somatoform disorders for the new version of the American Diagnostic and Statistical Manual of Mental Disorders to propose the term ‘Complex Somatic Symptom Disorder’. Debate continues about the number of symptoms required to reach the threshold for this diagnosis, but it is clear that health-related anxiety will be part of the criteria. Third, many patients who have unexplained symptoms often present with more than one symptom. Some symptom clusters are diagnosed as a functional somatic syndrome, such as chronic fatigue syndrome, fibromyalgia and irritable bowel syndrome. In fact, there is considerable overlap of symptoms between these and other functional somatic disorders. The eventual diagnosis is largely determined by which medical specialty the patient is referred to rather than the set of symptom complaints because each medical specialty has at least one term for these patients. Fourth, mood and anxiety disorders may not be more common in people with MUD or associated with worse outcomes, but most patients with somatoform disorders have MUD and do not improve. Three or more general physical symptoms or unexplainable symptoms are positively associated with depression, anxiety, substance abuse, and service use and psychological distress. A significant mental health underpinning of any biopsychosocial concept of MUD is also supported by a number of other observations: Internal Medicine Journal 42 (2012)