Polymyalgia Rheumatica

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Polymyalgia rheumatica is by nature an inflammatory disorder predominantly characterized by muscle pain in the neck and shoulders, but also in the upper arms, hips, and thighs. It typically has a rapid onset that occurs over a period of days. The initial symptom is usually shoulder pain, followed by pain in the neck, lower back, buttocks, hips, or thighs. Individuals may also experience tenderness in their upper arms, as well as pain or stiffness in the wrists or knees. The affected areas are usually also plagued with stiffness, which is often worse upon awakening or after periods of prolonged inactivity, such as sitting for a long period of time. At the time initial symptoms appear, many individuals will also experience additional non-specific symptoms, such as a low-grade fever, anemia, fatigue, general ill-feeling, appetite loss, unexpected weight loss, and even depression. Collectively, the symptoms of polymyalgia rheumatica can impair an individual’s ability to perform normal activities of daily living, including dressing, bathing, and driving. As a result, these limitations can have a significant negative impact on individuals’ health, social engagement, mental status, and physical activity level.

One of the most prominent risk factors for polymyalgia rheumatica is age. Polymyalgia rheumatica tends to affect those over age 65, with an average age of onset at 70 years. Individuals under age 50 are rarely affected. Another risk factor is sex, with women more likely to be affected than men at a rate of two to one.

The pain and stiffness involved in polymyalgia rheumatica result from the over-activity of inflammatory cells and proteins in the body’s immune system. This inflammation tends to be localized to the tissues that surround the affected joints, and radiates pain outward to the surrounding muscles, resulting in what is known as “referred pain.” Despite this understanding of the mechanisms underlying the pain and stiffness, the exact cause of polymyalgia rheumatica – i.e., what triggers the overactive inflammatory response within the body – is not well understood.

A combination of both genetic and environmental factors are believed to be involved in its development. For example, polymyalgia rheumatica is more prevalent among individuals of Northern European ancestry (in particular Scandinavia), and its patterns of family history are suggestive of a genetic predisposition as well. In terms of potential environmental factors, various viral infections have been suggested as playing a role in the onset of polymyalgia rheumatica. This theory is suggested not only because of the sudden onset of its associated symptoms (which can be indicative of an underlying infection), but also in light of the fact that new cases of polymyalgia rheumatica often appear in cycles in the general population, similar to the way common viral infections do.

Another inflammatory disease – giant cell arteritis (or temporal arteritis) – is also characterized by over-activity of many of the same immune cells and proteins that are involved in the inflammation seen with polymyalgia rheumatica. Giant cell arteritis results in inflammation of the lining of arteries in the temples, and causes symptoms such as headaches, jaw pain, scalp pain, and impaired vision (which can lead to permanent loss of vision). It can also lead to heart attack and stroke. Some researchers believe that polymyalgia rheumatica and giant cell arteritis are actually variants of the same disease process due to the significant overlap seen in their diagnoses. For example, up to 20% of individuals with polymyalgia rheumatica have giant cell arteritis, whereas as many as 60% of individuals with giant cell arteritis also have polymyalgia rheumatica.

There is no cure for polymyalgia rheumatica, however sustained therapy with low dose corticosteroids (such as prednisone) can prevent disability in many individuals. However, steroid therapy is usually needed for several years, which can cause serious side effects. These include osteoporosis (the loss of bone mass and generalized weakening of bones), high blood pressure, high cholesterol, diabetes, cataracts (clouding of the lens of the eye), and depression. The osteoporosis can be prevented somewhat through supplementation with both calcium and vitamin D, and physical therapy may also be recommended to help individuals maintain (or regain) mobility, strength, and coordination.

Polymyalgia Rheumatica and Fibromyalgia

Individuals with widespread musculoskeletal pain – such as those with fibromyalgia or polymyalgia rheumatica – are frequently seen by rheumatologists during their search for a diagnosis. Due to the subjective nature of widespread pain, and the lack of specificity of its associated symptoms, the door must be left open for other conditions to be considered during the diagnostic process. This is important in order to accurately identify the active disease process and prevent unintentional injury to joints, muscles, and tissues.

Polymyalgia rheumatica and fibromyalgia share a number of common symptoms and can mimic each other in terms of presentation, therefore both conditions should be considered in the diagnostic setting when evaluating a patient with widespread musculoskeletal pain  (Hwang & Barkhuizen, 2006; Daoud & Barkhuizen, 2002; Reilly, 1999; Hench, 1989).

In particular, both fibromyalgia and polymyalgia rheumatica are characterized by widespread pain at various anatomical sites, and many fibromyalgia tender points overlap with the sites most often affected by polymyalgia rheumatica. Furthermore, joint stiffness – in particular during the morning hours – is a common symptoms of both conditions, as are depression and fatigue. Both conditions are more likely to occur among women and can also run in families.

The diagnosis of fibromyalgia is usually quite cumbersome and involved, and relies more or less on the exclusion of a number of related conditions and others – such as polymyalgia rheumatica – that can mimic it symptomatically. On the other hand, polymyalgia rheumatica can usually be diagnosed through a combination of blood tests (in particular, measurements of the erythrocyte sedimentation rate [ESR or Sed rate] and C-reactive protein), as well as imaging tests (such as ultrasound) to visualize internal areas of inflammation, as well as a comprehensive physical exam. In addition, once steroid therapy has been initiated, relief is usually obtained after several days of treatment. Therefore, individuals who do not respond to corticosteroid therapy within a few days likely do not have polymyalgia rheumatica. As such, response to therapy is another way by which doctors are able to confirm the diagnosis.

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References

1.        Hwang E, Barkhuizen A. Update on rheumatologic mimics of fibromyalgia. Curr Pain Headache Rep. 2006;10(5):327-332.

2.        Daoud KF, Barkhuizen A. Rheumatic mimics and selected triggers of fibromyalgia. Curr Pain Headache Rep. 2002;6(4):284-288.

3.        Reilly PA. The differential diagnosis of generalized pain. Baillieres Best Pract Res Clin Rheumatol. 1999;13(3):391-401.

Hench PK. Evaluation and differential diagnosis of fibromyalgia. Approach to diagnosis and management. Rheum Dis Clin North Am. 1989;15(1):19-29.

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