The diagnosis of fibromyalgia (FM), a chronic disorder characterized by widespread pain and tenderness, was made clinically based on the characteristic medical history and physical examination findings.
Fibromyalgia affects approximately 5 million Americans, 80%-90% of those who are diagnosed with the disease are women aged 20-55 years. The diagnosis of fibromyalgia should be made based on the specific criteria for the disease and the patient's presentation, as well as on exclusion of differential diagnoses. For the condition to be diagnosed, chronic symptoms must have been present for over three months. Widespread pain and tenderness must be reported both above and below the waist, as well as along the axial spine bilaterally. Associated symptoms include fatigue, sleep disturbances, and cognitive or mood disorders that result in impairment of activities of daily living (ADL). Patients have a lifetime prevalence of depression and anxiety of 74% and 60%, respectively.
The etiology of FM is still being elucidated; however, it is multifactorial (Figure 1). The condition seems to involve disordered central pain processing and hypersensitivity that leads to a lower threshold of pain, heat, cold, and other stimuli that register as pain.
Quantitative sensory studies using various stimuli and functional magnetic resonance imaging (fMRI) evaluated the pattern of cerebral activation in patients with fibromyalgia compared with controls. The results suggested that fibromyalgia is associated with cortical and subcortical augmentation processing. Pain-processing abnormalities suggested in FM include hypersensitivity of N-methyl-D-aspartate (NMDA) receptors, dysregulation of dopaminergic neurotransmission and of the hypothalamic-pituitary axis, decreased levels of inhibitory neurotransmitters (serotonin, norepinephrine), and increased levels of excitatory neurotransmitters (substance P, glutamate).[6,7]
The American College of Rheumatology published criteria that allow physicians to diagnose fibromyalgia with a carefully taken history in addition to a physical examination, without the need for specialized training. The criteria include a Widespread Pain Index (WPI) and a Symptom Severity Index (SSI). The WPI documents whether the patient has had pain or tenderness in 19 different areas of the body over the previous week and quantifies the pain on a scale of 0-19. (Figure 2 shows tender points.)
The SSI quantifies severity of fatigue, trouble sleeping, and memory impairment on a scale of 0-12. A diagnosis of fibromyalgia is made if symptoms have been present for at least three months, the WPI score is 7 or higher, and the SSI score is 5 or higher.
The initial workup should include a CBC, BMP, and UA, as well as thyroid screening to rule out hypothyroidism as the etiology of the fatigue. Those test values are usually within normal limits in fibromyalgia. Based on the patient's clinical presentation, clinicians should also consider that the patient is suffering from low levels of vitamin D (which cause muscle pain and depression), vitamin B-12 (which cause pain and fatigue), iron (which cause fatigue and restless leg syndrome), or magnesium (which cause fatigue). Imaging modalities are not necessary in the diagnosis of fibromyalgia.
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