Polymyalgia Rheumatica

CHAPTER 127

Polymyalgia Rheumatica

Presentation

An elderly patient (more commonly female) complains of aching pain and stiffness of the proximal extremities. Shoulder pain and stiffness are most common, followed by the pain and stiffness in the hips, neck, and torso. The onset of symptoms is generally acute, but patients often do not seek professional help for more than a month. The pain and stiffness are characteristically worse in the morning, making it difficult to rise from bed, but improve throughout the day. Approximately one third of patients complain of constitutional “flulike” symptoms, including malaise, fatigue, anorexia, weight loss, and low-grade fever. A patient may ascribe her problem to muscle weakness or joint pains, but physical examination discloses that bilateral symmetric pain and tenderness of neck, shoulder, and hip muscles are the actual source of any “weakness.” The patient may demonstrate limited active range of motion of the affected joints, but full passive range of motion and normal strength are typically present. There may be some mild arthritis of several peripheral joints, but the rest of the physical examination is negative, other than the finding of a patient who appears fatigued and uncomfortable.

What To Do:

Perform a complete history and physical examination, particularly of the cervical and lumbar spine and nerve roots (strength, sensation, and deep tendon reflexes in the distal limbs should be intact with polymyalgia rheumatica [PMR]). Confirm the diagnosis of PMR by palpating tender shoulder muscles (perhaps also hips and, less commonly, neck).

Consider other diseases that can mimic PMR. These include polymyositis, drug-induced myopathies (e.g., statins), hypothyroid myopathy, systemic lupus erythematosus, rheumatoid arthritis or other arthritides, bacterial endocarditis, fibromyalgia, depression, cervical or lumbar radiculopathies, and various malignancies or paraneoplastic syndromes.

Confirm the diagnosis by obtaining an erythrocyte sedimentation rate (ESR), which should be in the 40 to 100 mm/hr range. (An especially high ESR, over 100 mm/hr, suggests more severe autoimmune disease or malignancy.) The classic laboratory finding in PMR is an ESR greater than 40 mm/hr. Elevation of the ESR is the only published laboratory criterion for diagnosing PMR.

Two retrospective studies have found that as many as 20% of patients with PMR may present with a normal or only mildly elevated ESR (≥40 mm/hr). A normal ESR in the setting of a clinical diagnosis of PMR may indicate a milder form of the disease. With such patients, a C-reactive protein (CRP) level may be useful. CRP (normal value <0.5 mg/dL) is also typically elevated in PMR. One study has demonstrated that CRP is more sensitive than ESR in assessing disease activity in a diagnosis of PMR, but this test is not considered part of the published diagnostic criteria for PMR.

Diagnostic criteria for PMR include age older than 50 years; bilateral aching stiffness of the shoulders, neck, or pelvic girdle for more than 1 month; morning stiffness lasting longer than 1 hour; an ESR greater than 40 mm/hr; and the absence of any other disease—except giant cell arteritis (GCA) (also known as temporal arteritis)—that may cause similar symptoms, such as polymyositis or rheumatoid arthritis. An additional criterion: prompt response to daily treatment with at least 20 mg of prednisone.

Always check for tenderness over the temporal arteries in patients with PMR to help rule out GCA. Patients with PMR should be evaluated for clinical signs of GCA, and vice versa. New-onset headache or scalp pain in any patient older than 50 years of age must raise clinical suspicion of GCA. Jaw claudication, generally characterized as fatigue and pain of the muscles of mastication, is one of the most specific signs of GCA. Initial presentation may be of transient visual loss or amaurosis fugax. Diplopia may also be an early manifestation of GCA. Biopsy of the temporal artery remains the standard for diagnosis of GCA and should be performed in any patient with a high suspicion of GCA. Positive biopsy findings typically show granulomatous inflammation of the vessel wall with infiltration of multinucleated giant cells, macrophages, and T cells.

Corticosteroids are the cornerstone of treatment of PMR. The usual starting dose of prednisone is 10 to 20 mg daily. This is continued for 1 month and is carefully tapered by 1 to 2.5 mg monthly to a dosage of 10 mg daily, based on clinical response. The dosage may be further tapered by 1 mg every 4 to 6 weeks to a maintenance dose of 5 to 7.5 mg daily.

Failure to achieve a prompt and complete response to corticosteroid therapy should initiate a search by the clinician for a different cause of the symptoms, such as another rheumatic condition or an occult malignancy.

Discontinuation of steroids may be attempted after 6 to 12 months if the ESR has normalized and the patient is symptom free. This is usually accomplished by continuing to taper the dosage by 1 mg every 6 to 8 weeks. Relapses are most common in the first 18 months of therapy.

The starting dose of glucocorticoids for GCA patients has not been definitively established. The current recommendation is to start these patients on 40 to 60 mg of prednisone daily. The average GCA patient requires 24 or more months of corticosteroid treatment.

Explain the syndrome to the patient and arrange for follow-up.

What Not To Do:

Do not order diagnostic imaging methods such as MRI or ultrasonography to confirm the diagnosis of PMR. These studies are usually not indicated in the evaluation of PMR.

Do not miss temporal arteritis (GCA), a common component of the PMR syndrome and a clue to the existence of ophthalmic and cerebral arteritis, which can have dire ophthalmologic and neurologic consequences. Palpate the temporal arteries for tenderness, swelling, or induration, and ask about transient visual or neurologic signs.

Do not postpone diagnosis or treatment of temporal arteritis pending results of a temporal artery biopsy showing giant cell arteritis. The lesion typically skips areas, making biopsy an insensitive diagnostic procedure. The progression to permanent visual loss has been found to occur in an average of 8.5 days after the onset of early symptoms (such as blurring, diplopia, or amaurosis fugax), and therefore immediate treatment may be critical. The accuracy of the biopsy will not be affected within a few weeks of initiating corticosteroid treatment.

Discussion

Polymyalgia rheumatica (PMR) is a systemic inflammatory disease that occurs in patients older than 50 years of age and is characterized by an elevated ESR, proximal extremity pain, morning stiffness, and rapid relief with the administration of corticosteroids. Giant cell arteritis, also known as temporal arteritis, is an inflammatory vasculitis of large and medium vessels primarily arising from the aortic arch. It occurs in adults older than 50 years of age and is characterized by headache, jaw claudication, and visual loss.

Many experts consider these two diseases to be points along a continuum of a specific systemic inflammatory disease syndrome, with PMR being the expression of a milder form of disease and GCA suggesting more severe disease. Both conditions are diseases of the elderly population, occurring exclusively in persons older than 50 years of age and peaking in incidence between 70 and 80 years of age. Women are affected twice as often as men, and whites of Northern European descent are most often predisposed to having these diseases. Various mechanisms have been postulated as causes of PMR, but the exact cause is unclear.

The disorder can generally be distinguished from other diseases on the basis of clinical presentation, laboratory evaluation, response to steroid therapy, or diagnostic imaging.

Stiffness, pain, and weakness are common complaints in many older patients, but polymyalgia rheumatica may respond dramatically to treatment. Rheumatoid arthritis produces morning stiffness but is usually present in more peripheral joints and without muscle tenderness. Polymyositis is usually characterized by increased serum muscle enzymes with a normal ESR and may include a skin rash (dermatomyositis). Often, a therapeutic trial of prednisone helps make the diagnosis. Giant cell arteritis can be a serious and, occasionally, fatal illness, with sudden irreversible visual loss, permanent hearing loss, or aortic dissection. Permanent visual loss occurs in approximately 15% of patients with GCA. Larger doses of corticosteroids are required than for polymyalgia rheumatica.

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