Lessons in herding zebras

Proper diagnosis is a key issue in ME/CFS. In the absence of a full clinical assessment (which most patients have either never undergone, or last had many years ago), the diagnosis of ME/CFS can easily become a terminal stop for clinically complex patients with a variety of different illnesses.

Some examples illustrate the problems that can arise if investigations to exclude other conditions are not performed before the ME/CFS ‘diagnosis of exclusion’ is given to the patient. The first is an audit of 100 outpatients with CFS in the University of Dundee in 1993: of these, 21% were found to have other organic illnesses (e.g., muscle, connective tissue or endocrine disorders), 12% had a psychiatric disorder alone, and 7% had fibromyalgia. The second example is an audit of service in 2007 after three years at the CFS/ME CNCC in Newcastle, England: CFS was confirmed in 56% of referrals, but alternative diagnoses were provided in 28%, sleep apnoea was diagnosed in 9%, and depression and anxiety in 7%. Subsequently, two studies have shown that alternative exclusionary diagnoses can be found after investigation at a specialist clinic in around 40% of patients referred in the UK from primary care with a diagnosis of CFS.

A fascinating commentary in an issue of Minnesota Medicine in 2008 describes the difficulties experienced at a clinic seeing patients with fatigue, exercise intolerance and weakness (i.e., patients very like those with ME/CFS in the UK). The authors report three recent cases, all adolescent patients experiencing fatigue and weakness, to illustrate how patients with common symptoms can end up with very different, sometimes unusual, diagnoses.

In the first case, an almost housebound 15-year-old girl with fatigue for 18 months following fever was eventually diagnosed with postural orthostatic tachycardia syndrome, which the authors say probably accounts for most cases of chronic fatigue during adolescence. The second case was a 14-year-old boy with exercise intolerance who was at times overwhelmed by weakness, palpitations and headaches. After full investigation, a renal ultrasound revealed masses near the kidneys, and the child has done well after surgical excision of these pheochromocytomas. In the final case, a 14-year-old boy presented with a three-month history of fatigue, weakness and weight loss, which finally resulted in a diagnosis of previously undiagnosed dermatomyositis and secondary bronchiolitis obliterans organising pneumonia, with the comment from the authors that “a thoughtful and thorough physical exam can sometimes reveal otherwise hidden diagnoses”.

In their conclusion, the authors say, “Sometimes in our clinic, we feel as if we’re wandering through a herd of zebras… Not all the ‘stripes’ on the animals are the same, and not every animal in the herd is actually a zebra… Navigating through clinical complexities is difficult, and we’re still learning how to best diagnose and manage our patients.” Commentaries like this do raise the question of which alternative treatable diagnoses might be uncovered if all patients currently parked in the ME/ CFS diagnostic terminal were examined intensively at a specialist Centre of Excellence by thoughtful and thorough physicians.

Reference: Fatigue, exercise intolerance, and weakness: lessons on herding zebras. Fischer PR, et al. Minn Med 2008 Nov; 91(11): 38-40.

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