Musculoskeletal pain is the one of the most common reasons for medical consultations in the community. Nonarticular rheumatic pain syndromes (eg, tendinitis, bursitis, enthesitis, or muscular tear) constitute a major proportion of these consultations. In most cases, these conditions are self-limited and respond to treatment.

Diffuse pain may be caused by inflammatory and noninflammatory conditions. Polymyalgia rheumatica (see Chapter 30), rheumatoid arthritis (see Chapter 15), and systemic lupus erythematosus (see Chapter 21) are common causes of diffuse inflammatory pain, while fibromyalgia and primary generalized osteoarthritis (see Chapter 43) are common causes of noninflammatory diffuse pain. Both inflammatory and noninflammatory diffuse pain conditions sometimes occur in the same patient, causing confusion in diagnosis and treatment. Because inflammatory conditions are covered elsewhere in this book, fibromyalgia is the main focus of this chapter.

Although some experts argue that fibromyalgia is not a distinct disease entity and that labeling patients with the diagnosis encourages chronic illness behavior and increases healthcare consumption, data from the General Practice Research Database has shown this premise to be false. The General Practice Research Database has collected information from over 750 practices, with more than 3 million patients and 35 million patient years of data. Based on this data, a 2006 study showed that healthcare utilization among fibromyalgia patients was already very high in the 8 years preceding the diagnosis. Furthermore, healthcare utilization decreased after diagnosis, indicating that the diagnosis could be used constructively to reassure and educate patients.

Essentials of Diagnosis

• Diffuse pain for longer than 3 months. Pain is defined as above and below the waist bilaterally; axial skeletal pain must also be present.
  
• Increased tenderness to light pressure (allodynia).
  
• Fatigue and nonrestorative sleep.
  
• Depression and anxiety disorders are common, but mood disorder is not universal and response to antidepressants is independent of any change in mood.

Fibromyalgia is one of the most common causes of chronic diffuse pain. It is associated with increased tenderness to light pressure (allodynia). Although the term fibromyalgia has only been used in the last 2 decades, it is not a new disease. In 1850, Froriep described hard places in the muscles of patients with “rheumatism” that were painful to light touch. Gowers used the term fibrositis to describe patients who complained of tenderness with light pressure in the absence of any signs of local or systemic inflammation. Subsequently, fibrositis was found to be a common cause of muscular pain, although many clinicians considered it as “psychogenic rheumatism.”

Patients with fibromyalgia have altered pain processing compared to normal individuals. This includes greater subjective pain, decreased pain threshold, increased pain ratings, and a steeper rise of response to repeated stimulation. These abnormalities have been attributed to an underlying central sensitization. Central sensitization is a term denoting a state of enhanced, or amplified, neural processing within the central nervous system. The normal physiologic role of central sensitization is thought to protect an injured area from further damage and maximize healing by immobilization. Central sensitization may involve the abnormal ascending and descending pain pathways in the spinal cord. Consistent with this hypothesis is the finding that in patients with fibromyalgia, increased levels of substance P are found in the cerebrospinal fluid. Neuroimaging studies have shown different neuronal activation pattern in patients with fibromyalgia compared with controls, supporting the notion that pain processing is abnormal.

Symptoms and Signs

Pain

Pain is the dominant symptom and principal complaint in fibromyalgia. Most patients have suffered from pain for many years before seeking medical advice. In some cases, pain may start in childhood. The reason for seeking medical advice is often because pain has become widespread or more severe, and patients may find it difficult to cope. Typically, patients complain of “pain all over their body,” although often it starts in one or two areas and then spread to other parts of the body. The severity of pain may vary in difficult parts of the body and from day to day. Most often, patients complain of a chronic ache with occasional severe sharp spasms or electric shocks. Others describe their muscles as tense and liken it to being “tied in knots.”

Pain is often worsened by exertion or physical activities, although many patients also complain of spontaneous pain without any obvious precipitating factor. Simple analgesics, such as acetaminophen or nonsteroidal anti-inflammatory drugs, are rarely effective. Some patients notice pain is worsened by stress. Indeed, some patients associate the onset of the illness with a physical or emotional stressful event, such as an illness or road traffic accident.

For a patient to meet the 1990 or 2011 American College of Rheumatology (ACR) classification criteria for fibromyalgia (see Diagnostic Criteria below), he or she must have a history of diffuse pain lasting more than 3 months, defined as pain on both sides of the body and pain above and below the waist. In addition, axial skeletal pain (cervical spine, anterior chest, thoracic spine, or low back) must be present. Low back pain is considered lower segment pain.

Tenderness, an increased sensitivity to light touch or pressure (allodynia and hyperalgesia), is one of the characteristic features of fibromyalgia. Hyperalgesia is defined as excessively severe pain induced by a noxious stimulus, while allodynia is pain induced by an innocuous stimulus. In some patients, the slightest touch can make them recoil in pain. They have to avoid physical contact, including gentle patting by their partners. As pain is aggravated by physical activity, most patients find it disabling and limits their ability to perform routine household chores, especially shopping and cleaning. Those patients who are employed often find it difficult to cope at work.

Concomitant chronic painful conditions, such as migraine, noncardiac chest pain, heartburn, dysmenorrhea, and irritable bowel syndrome, are common in patients with fibromyalgia and may pre-date the diagnosis.

Fatigue

Fatigue is common in fibromyalgia, affecting 80–90% of patients. Typically, patients describe fatigue as an “overwhelming tiredness” and feeling “completely washed out.” In some patients, severe episodic attacks may come on suddenly. Some patients find it more difficult to cope with the fatigue than with the pain, since rest and sleep rarely improve fatigue. Although many patients complain that fatigue is a disabling symptom, it is less severe and disabling than in chronic fatigue syndrome. When fatigue is overwhelming and the muscular pain is less prominent, chronic fatigue syndrome should be considered as an alternative diagnosis.

Nonrestorative Sleep

Nonrefreshing sleep is a feature of fibromyalgia in over 90% of patients. In most patients, it is not insomnia; they can fall asleep, but they do not feel refreshed in the morning, which is due to poor sleep quality. Often, poor sleep quality is associated with feeling tired and difficulty in performing physical activity and poor cognitive performance. In addition, some fibromyalgia patients complain of sleepiness during the day. Other patients complain of waking up frequently during the night. Some patients also suffer from restless leg syndrome. Impaired sleep quality was found to be predictive of pain, fatigue, and social functioning in one study. Polysomnographic studies have found correlation between sleep disturbance in patients with fibromyalgia with specific patterns of alpha intrusion and decrease slow wave sleep, suggesting “wakefulness” or lack of quality deep restful sleep may be an important part of the pathophysiology. Indeed, inducing sleep disturbance in healthy individuals can cause myalgia and increase tenderness. However, loud snoring and disturbances of breathing during the night are uncommon in fibromyalgia; the presence of these symptoms should alert clinicians to possible primary sleep disorders, such as obstructive sleep apnea. These patients may need referral to sleep clinics for further evaluation.

Depression and Anxiety

History of depression and anxiety disorders is common in patients with fibromyalgia. The prevalence of concomitant depression and anxiety is higher among patients in secondary care than those in the community. This contributes significantly to the view among specialists that mood disorders are the cause of fibromyalgia. However, epidemiologic studies showed that mood disorder is not universal and response to antidepressants in patients with fibromyalgia is independent of any change in mood. These studies suggest that mood disturbance is not the sole pathogenic factor in most patients with fibromyalgia. In patients with fibromyalgia, depression is often associated with more severe fatigue as well as poor sleep quality and pain control. Patients with anxiety often experience palpitation and dizziness, sweating, and paresthesia. In severe cases, some patients may experience panic attacks. Occasionally, some patients may have severe depression, so it is important to assess mood and suicidal risk. Patients with severe depression and those with suicidal thoughts need urgent referral to a psychiatrist.

Impaired Cognition

Cognition problems are common in patients with fibromyalgia. Poor short-term memory as well as difficulty in learning a new task, processing information, and problem solving are common complaints. Many patients describe suffering from “brain fog.” In many cases, impaired cognition occur as episodic attacks and last for a few hours or days, although in some cases, they may be more prolonged. Impaired cognition is a major contributor of frustration and psychosocial stress, especially in patients whose employment is mentally demanding.

Morning Stiffness

Traditional prolonged early morning stiffness is regarded as a symptom of inflammatory disorders, such as rheumatoid arthritis. However, patients with fibromyalgia also suffer from prolonged early morning stiffness, resulting in diagnostic confusion with inflammatory arthritis, especially if they also complain of swollen hands or feet. One of the distinguishing features of early morning stiffness in fibromyalgia is that it is not relieved by exercise. Furthermore, although patients may complain of swelling in the hands and feet, objective evidence of synovitis is lacking, and the patient points to more diffuse swelling rather than discrete swelling around the joints.

Other Symptoms

Patients with fibromyalgia may complain of symptoms affecting other systems, including gastrointestinal (nausea, vomiting, bloating, abdominal pain, diarrhea, and constipation), urogynecologic (urgency, frequency, incontinence, pelvic pain, and dysmenorrhea), and neurologic (dizziness, vertigo, paresthesia, and tinnitus).

However, fever, weight loss and swollen lymph glands are rare. The presence of these suggest an alternative diagnosis.

Physical Examination

The goal of the physical examination is to confirm diagnosis and rule out other differential diagnoses, which are listed in Table 14–1.