Polymyalgia RheumaticaDz

ICD-9 Code: 725.0.

ICD-10 Code: M35.3

Definition: Polymyalgia rheumatica is an inflammatory disorder of older white adults that causes pain and stiffness in the proximal musculature.

Etiology: The cause is unknown. It has a strong association with some HLA markers, especially HLA-DR4. As in RA, the genotype HLA-DRB1*04 more commonly occurs in polymyalgia rheumatica than in the general population. Seasonal clustering of polymyalgia rheumatica and a preponderance in people of northern latitudes may provide etiopathogenetic clues.

Pathology: No well-defined pathologic lesion has been identified in either muscle or surrounding joints. Arthroscopic synovial biopsy of the shoulders in affected patients has shown low-grade synovitis, suggesting a link with large-joint arthritis.

Demographics: The prevalence of polymyalgia rheumatica approaches that of RA in older populations. It is almost twice as common in women as in men, and it occurs preferentially in adults of northern European ancestry. It is rare in nonwhites. Approximately 85% of patients with polymyalgia rheumatica are older than 60 years of age. It is estimated that there are 400,000 to 700,000 patients with polymyalgia rheumatica in the United States. The annual incidence for those older than 50 years is 59 cases per 100,000.

Cardinal Findings: Onset before the age of 50 is highly unusual. Symptoms may begin abruptly or insidiously as pain, stiffness, and tenderness in the neck, hip, and shoulder girdle. Prolonged morning stiffness is also characteristic. Associated constitutional symptoms often include anorexia, fatigue, weight loss, low-grade fevers, and occasional night sweats. Synovial swelling is seen in 20% to 35% and may occur in the wrists, knees, and small joints of the hands. Polymyalgia rheumatica commonly overlaps with late-onset RA.

Complications: Progression from polymyalgia rheumatica to giant cell arteritis is seen in 10% to 13% of patients with polymyalgia rheumatica. Nonetheless, blind temporal artery biopsies should not be done in these patients. Progression to RA is seen in >15%, thus distinguishing between polymyalgia rheumatica and RA is difficult.

Diagnostic Testing: A moderately to markedly elevated ESR (usually >60 mm/h) or CRP is highly characteristic. Anemia of chronic disease, leukocytosis, reactive thrombocytosis, and decreased albumin are also common. Alkaline phosphatase and hepatic enzymes may be elevated. Factor VIII/von Willebrand factor and other endothelium-derived proteins also may be elevated in patients with polymyalgia rheumatica, but testing is not clinically indicated.

Radioisotope scans have identified synovitis in large joints but are not of any diagnostic value.

Keys to Diagnosis: Look for abrupt onset of soreness in the shoulder and hip girdle muscles with stiffness, fatigue, and elevated ESR in an older white person. Polymyalgia rheumatica may present as fever of unknown origin or an occult cause for anemia or weight loss.

Differential Diagnosis: A myriad of other systemic inflammatory, infectious, and neoplastic disorders can present with similar protean symptoms. Hypothyroidism is a frequent consideration. Polymyalgia rheumatica is differentiated from inflammatory myopathy (DM and PM) by the absence of frank muscle weakness or characteristic skin and other nonmusculoskeletal findings. Unlike fibromyalgia, polymyalgia rheumatica has significant evidence of systemic inflammation, with laboratory testing abnormalities.

Therapy: Initial treatment with low- to moderate-dose corticosteroid (prednisone, 10–20 mg/day) is highly effective in relieving symptoms. A significant response to prednisone within 2 to 3 days may be diagnostically helpful. Once symptoms are well controlled, corticosteroids may be tapered by approximately 1 to 2 mg/mo. Studies show that only 24% to 40% of patients are able to wean off prednisone after 24 months of therapy, and no suitable alternative for steroids has been proven. Although steroid-sparing agents are sometimes considered, none (e.g. MTX) are of proven value. Hydroxychloroquine has occasionally been used to treat polymyalgia rheumatica coupled with late-onset RA. NSAIDs may be added to help control mild inflammatory symptoms once the prednisone dose is 10 mg/day or less.

Prognosis: Although it may impose substantial disability, polymyalgia rheumatica itself is not a life-threatening illness. Nonetheless, considerable morbidity may result from long-term corticosteroid therapy.

BIBLIOGRAPHY

Bird HA, Esselinckx A, Dixon ASJ, et al. An evaluation of criteria for polymyalgia rheumatica. Ann Rheum Dis 1979;38:434–439.PMID:518143

Calvo-Romero JM. Giant cell arteritis. Postgrad Med J 2003;79:511–515.PMID:13679546

Chuang T-Y, Hunder GG, Ilstrup DM, et al. Polymyalgia rheumatica: a ten year epidemiologic study. Ann Intern Med 1982;97:672–680.PMID:6982645

Hazleman BL. Polymyalgia rheumatica and giant cell arteritis. In: Hochberg MC, Silman SJ, Smolen JS, eds., et al., Rheumatology, 3rd ed. Edinburgh: Mosby, 2003:1623–1633.