Fibromyalgia: Practical Approaches To Diagnosis and Treatment
Fibromyalgia (FM) syndrome is a common clinical disorder that is characterized by chronic widespread pain. Although pain is the most prominent symptom, there are many other manifestations that mix and match as they contribute importantly to the morbidity of FM.
Gone are the days when FM was considered a psychological disorder. Growing objective evidence shows that FM is a disorder of the central nervous system. Much is known about its clinical presentation, diagnosis, pathogenesis, epidemiology, natural history, and treatment. Thus far, the FDA has approved three mechanism-based medications to treat FM.
The challenge for the future is to identify symptomatic patients earlier in their clinical course in hopes of reducing the potential for development of long-term disability.
The goal of this two-part series is to provide a practical, quick, and easy summary of FM. This installment focuses on the epidemiology of FM and discusses new diagnostic criteria endorsed by the American College of Rheumatology (ACR). In Part 2, we review treatment strategies for managing patients with this disease.
Epidemiology of Fibromyalgia
It has been estimated that FM affects approximately 2% of the general population, or about 5 million Americans.1 The disorder is found in all ethnic groups and is not limited to developed or industrialized countries. Adult women are up to seven times more likely than adult men to have FM, and the prevalence of the disorder increases with age, most dramatically in women with a peak in the fifth to seventh decade (7.4%-10%).1 The risk for having or developing FM in a family with one affected member is about 8.5-fold greater than in a family without any affected members.2 Although seen most commonly in middle-aged women, FM also is seen in children and teenagers.3-5 (For a review of juvenile FM, please see related article on page 81.)
Researchers have identified a number of risk factors for the development of FM, including the following:
- Familial/genetic predisposition3,6
- Physical trauma.7 (People with whiplash are more likely to develop systematic FM than industrial accidents limited to lower extremity fracture; 22% vs. 2% for all subjects, >30% for female accident victims.)8 Narrowed cervical canal may be an important risk factor for the development of chronic pain and cord pathology following a whiplash injury.9,10
- Major febrile illness
Classification of Soft Tissue Pain Syndromes
Fibromyalgia is just one of more than 200 musculoskeletal conditions that can cause body pain and interfere with mechanical function. It is logical to divide these into two nearly equal categories of those that actively involve the joints (eg, arthritis) and those that do not.
There has been much confusion in terminology surrounding the arthritis group where joint involvement is not the focus. Some of the confusion results from misunderstanding about the myofascial pain syndrome (MPS). Clinicians who have heard of MPS but are not skilled in its diagnosis often use the term myofascial pain generically. A better umbrella term is soft tissue pain (STP).11 It can be used in clinical charts as both a historical and an examination category.
Table 1 provides a useful classification of STP with three main subheadings:
1. Local conditions: Most are believed to result from repetitive mechanical injury to inadequately conditioned tissues. They are named anatomically and can be disclosed by a typical history of localized pain plus exquisite tenderness of the affected structure elicited by firm digital palpation. Examples include biceps tendinitis and trochanteric bursitis.
2. Regional syndromes are limited in anatomic scope to a region or quadrant of the body, as seen with MPS and complex regional pain syndrome (CRPS).
3. The generalized category implies a systemic process like that of FM, which affects the musculoskeletal system in a more global manner. There is no clear evidence to suggest that a localized STP condition can evolve into a regional STP condition or that any of the regional STP disorders can morph into a generalized category condition. Examples include FM and chronic fatigue syndrome when it is painful, hypermobility syndrome.
Making the Diagnosis
The 1990 ACR Criteria
Early in the course of FM studies, the condition was called fibrositis and each investigator had developed diagnostic criteria that seemed to apply. That situation changed when a collaborative research study led to the 1990 ACR Research Classification Criteria (ACR RCC) for fibromyalgia.12 It is emphasized that these criteria were intended to identify subjects for research study but not for medical care.
Two components were required: one from the patient’s medical history (chronic widespread pain for at least 3 months) and one from the physical examination (11 of 18 painfully tender soft tissue sites) (Table 2).
2010 ACR Diagnostic Criteria
Both components of the 1990 ACR RCC were based on the domain of pain in FM but they completely ignored the comorbid domains, that are so troublesome to many patients with FM (Table 3).
There clearly was a need for validated clinical criteria that would also focus on FM comorbid manifestations such as sleep dysfunction, headache, cognitive dysfunction, affective manifestations, fatigue, chest pain, irritable bowel syndrome, and bladder irritability. On the basis of that need, a new approach to clinical diagnosis of FM was developed.12,13
As with the 1990 ACR RCC, the new criteria, called the 2010 ACR Fibromyalgia Diagnostic Criteria (2010 ACR FDC), were established from the results of a clinical study. The 2010 ACR FDC viewed the 1990 ACR RCC as the gold standard but did not require tender-point examination. Critically, the 2010 ACR FDC was validated for the setting of clinical medical care.
As with the 1990 ACR RCC, the 2010 ACR FDC has two components: the Widespread Pain Index (WPI) and the Symptom Severity Scale (SSS).