A 51-year-old woman comes to the clinic due to 6 months of fatigue and low back pain radiating to the buttocks. She also has persistent muscle pain in her arms and shoulders that worsens acutely after exercise. Physical examination shows normal muscle strength. Her joints are not swollen, but palpation over the outer upper quadrants of the buttocks, mid trapezius, and medial aspect of the knees elicits tenderness. C-reactive protein level is 3 mg/L (reference value <8 mg/L). Which of the following is the most likely diagnosis?
Distinguishing features of fibromyalgia, polymyositis & polymyalgia rheumatica | ||
Clinical features | Diagnosis | |
Fibromyalgia |
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Polymyositis |
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Polymyalgia rheumatica |
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ANA = antinuclear antibody; AST = aspartate aminotransferase; ESR = erythrocyte sedimentation rate. | ||
This patient has characteristic features of fibromyalgia (FM). FM occurs most commonly in young to middle-aged women and presents with widespread pain, fatigue, and cognitive/mood disturbances. Patients have a fairly normal physical examination except for trigger point tenderness in areas such as the mid trapezius, lateral epicondyle, costochondral junction, and greater trochanter. Patients perceive that their pain and fatigue worsen acutely after exercise, although a regular, incremental, low-impact exercise regimen (eg, fast walking, swimming, water aerobics) can improve pain and provide long-term benefit.
The diagnosis of FM is primarily based on history and examination findings. Revised 2010 American College of Rheumatology criteria suggest using the widespread pain index and symptom severity score for diagnosis, as these reflect the cognitive and somatic symptoms of the disorder better than criteria based on trigger points. Laboratory tests, including inflammatory (eg, erythrocyte sedimentation rate, C-reactive protein [CRP]) and serologic (eg, rheumatoid factor, antinuclear antibody) markers, are typically normal.
(Choices B and D) Although polymyalgia rheumatica (PMR) occurs at age >50 and can cause acute or subacute pain, it more commonly causes stiffness of the shoulders (~75%-90%) and pelvic girdle. Patients may have focal tenderness due to bursitis or synovitis; however, true muscle tenderness is unusual. Giant cell (temporal) arteritis frequently occurs in association with PMR and presents with headache, jaw claudication, and visual disturbances. Inflammatory markers are almost always elevated in these disorders, with sensitivity of CRP approaching 100%.
(Choice C) Polyarteritis nodosa presents with systemic symptoms, skin findings (eg, livedo reticularis, purpura), kidney disease, abdominal pain, and muscle aches or weakness. CRP is usually elevated.
(Choice E) Polymyositis is characterized by symmetrical proximal muscle weakness and elevated muscle enzymes (eg, creatine kinase, aspartate aminotransferase, aldolase). Pain is generally absent or mild.
(Choice F) Rheumatoid arthritis typically presents with pain and swelling in the wrists and small joints of the hands (eg, metacarpophalangeal, proximal interphalangeal), morning stiffness, and systemic symptoms. CRP levels correlate with disease activity.
(Choice G) Seronegative spondyloarthropathies (eg, ankylosing spondylitis) are most common in men age 15-35 and rarely present at age >45. Erythrocyte sedimentation rate and CRP are frequently elevated. Back pain in these disorders is typically worse with rest and better with activity, in contrast to FM, in which pain is acutely worse with exercise and only gradually diminishes with a regular exercise regimen.
Educational objective:
Fibromyalgia presents commonly in young to middle-aged women with widespread pain, fatigue, and cognitive/mood disturbances. Diagnosis is made clinically using the widespread pain index and symptom severity score, which emphasize cognitive problems, fatigue, and severity of somatic symptoms.