In a recent article in Arthritis Care & Research, Albert et al provided a concise and interesting review for rheumatologists on mitochondrial myopathies (1). The authors described 4 different categories of patient presentation, highlighted by 3 short cases. The article outlined clinical features compatible with a mitochondrial myopathy, a differential diagnosis, and tests to consider in such patients with an emphasis on muscle histology. The authors, however, did not include fibromyalgia syndrome in the differential diagnosis, which is particularly relevant to case 3 (1).
Fibromyalgia syndrome is a common disorder characterized by widespread pain in the muscles, bones, and joints, often with additional symptoms including fatigue, poor sleep, headaches and dizziness, irritable bowel syndrome, and cognitive difficulties (2–4). Elaborations on the original 1990 American College of Rheumatology criteria for the classification of fibromyalgia (2) have been published recently in Arthritis Care & Research (3). Many of the clinical features of fibromyalgia syndrome are not unlike those that the patient in case 3 presented with (1–5). In practice, the clinical suspicion for a diagnosis of fibromyalgia syndrome is often supported by the negative results of testing such as routine laboratory studies, imaging, and, when ordered, electromyogram studies (4). Clinicians familiar with this syndrome can diagnose the condition easily and confidently and usually do not order expensive or exhaustive diagnostic testing. Treatment is effective for the majority of patients (4–5).
Fibromyalgia is thought to affect somewhere between 0.5% and 4% of the general population (4–5). Fibromyalgia syndrome is a common diagnosis among patients referred to a rheumatology clinic (4, 5), whether as a primary syndrome or a diagnostic dilemma, and more frequently encountered than rare disorders like the idiopathic inflammatory myopathies, systemic lupus erythematosus, vasculitis, and, it would appear, mitochondrial myopathies. Therefore, we suggest that fibromyalgia syndrome should be included in the differential diagnosis of mitochondrial myopathies.
On a practical level, advice for rheumatologists on how to differentiate these 2 conditions and when to consider additional testing for mitochondrial myopathies in patients labeled as “fibromyalgia syndrome” would be very helpful.