Some illnesses are uncool. That might sound like an inflammatory comment – especially for a medical journal, yet perhaps the biggest concealed fact in medicine is that hierarchies of diseases exist among patients and healthcare professionals. A caste system of illness influences how patients perceive their health complaints, whilst health professionals also hold biases that influence how they treat and rank patients in the medical pecking order. When it comes to hierarchies of illness, evidence shows that chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME), features at the bottommost end of the medical “favoured” list. In the 1980s, newspapers helped coin the dismissive label “yuppie flu”; today, ME/CFS sufferers are still being referred to psychotherapists to work on their “faulty” illness beliefs. The truth about CFS/ME is that it is a medically contested illness; the NHS and NICE guidelines acknowledge that there are massive gaps in our current understanding around the illness, its cause and its impact on patients. CFS/ME is also illness that can devastate lives, leaving many housebound, bedbound and isolated, not just from society but also in terms of medical support. Acknowledgment about the limited knowledge about this illness (which, indeed, may turn out to be a cluster of different diseases or illnesses) is frequently overshadowed by disagreement about theoretical models of the aetiology and morphology of ME/CFS. Ramsay’s 1950s model of ME as a post-viral infection causing muscle weakness and neurological inflammation was challenged by psychiatrists McEvedy and Beard, as nothing more than mass-hysteria. ‘ME’ as a medical entity was later supplanted in the 1980s by psychiatrists such as Simon Wessely, replaced by the label ‘chronic fatigue syndrome’; a fatiguing syndrome of unknown origin that exists, in part, as a result of dysfunctional illness beliefs, as well as social trends and social care systems that reward illness seeking behaviours. Leaving aside medical controversies, what appears to have been forgotten is medicine’s duty of care. Studies consistently show that patients with CFS/ME routinely feel disbelieved, distressed, and deeply dissatisfied with their medical care. In our article [co-authored with Havi Carel] we aim to show that patients with ME/CFS are often dismissed and may even be harmed when doctors ignore or challenge the legitimacy of their illness experience. Research shows that many patients with ME/CFS feel marginalised, neglected, and drop out of mainstream medicine in despair. Our paper focuses on the marginalisation of the patient’s voice in the healthcare context by applying Miranda Fricker’s concept of ‘epistemic injustice’ to CFS/ME. For Fricker, there is an ethical imperative to share in the production and formation of knowledge. The healthcare encounter is an epistemological forum where the patient and doctor must combine their knowledge in order to arrive at well-formed medical decisions. In this epistemic scenario, the testimony and expertise of both the doctor and the patient are crucial to the outcome. Now clearly patients are not experts on every aspect of their illness – if they were, there would be no medical consultation. However, patients are experts about their first person experiences of living with medical symptoms – and not unusually, patients suffering from chronic conditions like ME/CFS are well-read and well-versed about their illness, including the kinds of treatments that work for them. This expertise should be of interest to doctors. Studies also show that doctors may view ME/CFS patients as hostile or combative when they challenge the incumbent biopsychosocial model of ME or CFS. Yet rather than feeling threatened or worse still, viewing the patient as uncooperative, there is an opportunity to discuss the limitations of medical knowledge. Here, we believe there is an ethical duty for candour and honesty: indeed, where there are clear gaps in medical knowledge the patient voice should have even more standing. In our paper, we find widespread evidence (in the literature) that ME/CFS patient testimony is devalued. Forms of exclusionary deflation may be unintentional but include ignoring patients’ views, undermining their testimony, and offering alternative explanations for their suffering (e.g. pain not being biological but somatised). We also find that exclusion is expressed as negative stereotyping (“heartsinky patients”), and by pernicious ways of psychologising patients’ worries and complaints (even labelling patients as “illness seeking”). Indeed, it is because of the incomplete knowledge of CFS/ME that patients may be especially vulnerable to insidious and harmful forms of ‘expert’ gap-filling. Our article hopes to highlight an ethical blind-spot in medical discourse to date: patients with CFS/ME suffer from a double whammy: not only is their medical condition unexplained, their very credibility as patients has been systematically deflated and discredited – even in the consulting room. The medical profession must be prepared to diagnose its own shortcomings, to better treat its patients.