Fibromyalgia

Fibromyalgia is a disease of the muscles. It is defined as "a common nonarticular rheumatic syndrome characterized by myalgia and multiple points of focal muscle tenderness to palpation (trigger points). Muscle pain is typically aggravated by inactivity or exposure to cold. This condition is often associated with general symptoms, such as sleep disturbances, fatigue, stiffness, headaches, and occasionally depression. There is significant overlap between fibromyalgia and the chronic fatigue syndrome (fatigue syndrome, chronic). Fibromyalgia may arise as a primary or secondary disease process. It is most frequent in females aged 20 to 50 years." (From Adams et al., Principles of Neurology, 6th ed, p1494-95)".

Etiology/causation

The cause is not clear; however, "patients with fibromyalgia experience pain differently from the general population".

Genetics

Using self-report of "Chronic Widespread Pain" (CWP) as a surrogate marker for fibromyalgia, the Swedish Twin Registry suggests a modest genetic contribution:

• Monozygotic twins with CWP have a 15% chance that their twin sibling has CWP
• Dizygotic twins with CWP have a 7% chance that their twin sibling has CWP

Abnormal sleep

Fibromyalgia is associated with alpha sleep. However, it is unclear if this abnormal sleep pattern causes or follows fibromyalgia.

Vitamin D deficiency

Low vitamin D levels may be associated with nonspecific musculoskeletal pain.

Diagnosis

Differential diagnosis

A cohort study found that widespread pain significantly increased risk of subsequent diagnosis of cancer, especially breast cancer and prostate cancer. The biological reason for this association is not clear.

Treatment

Clinical practice guidelines by the European League Against Rheumatism (EULAR) recommends (parentheses contain levels of evidence and strength of recommendation):
General

1. "Full understanding of fibromyalgia requires comprehensive assessment of pain, function and psychosocial context. Fibromyalgia should be recognised as a complex and heterogeneous condition where there is abnormal pain processing and other secondary features" (IV D)
2. "Optimal treatment requires a multidisciplinary approach with a combination of non-pharmacological and pharmacological treatment modalities tailored according to pain intensity, function, associated features such as depression, fatigue and sleep disturbance in discussion with the patient" (IV D)

Non-pharmacological management

1. "Heated pool treatment with or without exercise is effective in fibromyalgia" (IIa B)
2. "Individually tailored exercise programmes, including aerobic exercise and strength training can be beneficial to some patients" with fibromyalgia" (IIb C)
3. "Cognitive behavioural therapy may be of benefit to some patients with fibromyalgia" IV D)
4. "Other therapies such as relaxation, rehabilitation, physiotherapy and psychological support may be used depending on the needs of the individual patient (IIb C)

Pharmacological management

1. "Tramadol is recommended for the management of pain in fibromyalgia" (Ib A)
2. "Simple analgesics such as paracetamol and other weak opioids can also be considered in the treatment of fibromyalgia. Corticosteroids and strong opioids are not recommended (IV D)
3. "Antidepressants: amitriptyline, fluoxetine, duloxetine, milnacipran, moclobemide and pirlindole, reduce pain and often improve function, therefore they are recommended for the treatment of fibromyalgia" (Ib A)
4. Tropisetron, pramipexole and pregabalin reduce pain and are recommended for the treatment of fibromyalgia" (Ib A)

Pregabalin (Lyrica) is approved for use in the United States by the Food and Drug Administration (FDA) for fibromyalgia. As compared to placebo, pregabalin benefits about 1 of every 6 people who use it if they are similar to the patients in a randomized controlled trial. In this trial, 29% of the patients who took the drug had a reduction in their pain versus 13% of the patients who took placebo.