By Eve Wadsworth MD
Faculty Peer Reviewed
Polymyalgia rheumatica (PMR) is a condition that resembles several different disorders including osteoarthritis and can be difficult to diagnose. In addition to osteoarthritis, PMR can resemble conditions as diverse as depression, fibromyalgia, myopathic drug reactions, and malignancy. PMR, however, can be associated with dangerous consequences, namely blindness, and is responsive to well-established treatment regimens. As such, familiarity with PMR’s presentation and its unique features is critical so as to avoid serious complications that can result from a delayed or missed diagnosis.
PMR has a well-known association with temporal arteritis. PMR occurs in as many as 50% of patients who present with concurrent symptoms of temporal arteritis. (1) Temporal arteritis has a characteristic presentation that includes headache ipsilateral to the inflamed vessel; jaw claudication; and constitutional symptoms such as fever, night sweats, fatigue, and anorexia. Patients presenting later in the course of temporal arteritis will often complain of visual changes or loss, heralding the most serious consequence of temporal arteritis: blindness secondary to ischemic optic neuropathy. In a patient with said presentation and complaints of morning stiffness in the shoulder, hip, and girdle, physicians are likely to identify PMR in the setting of temporal arteritis. However, symptoms of PMR do not always occur at the same time as the symptoms of temporal arteritis, and PMR can occur completely independently of temporal arteritis. When it presents without the unique symptoms of temporal arteritis, PMR can present a diagnostic dilemma.
Familiarity with the full range of manifestations of PMR is imperative. In 1979, Howard Bird characterized the clinical features most helpful in the diagnosis of PMR by determining their specificity and sensitivity. Seven features were meaningful in their sensitivity or specificity for PMR: shoulder pain and/or stiffness bilaterally, onset of illness of <2 weeks duration, initial ESR >40 mm/hr, morning stiffness duration of >1 hour, age >65 years, depression and/or loss of weight, and upper arm tenderness bilaterally. Dr. Bird and his colleagues proposed that the presence of three or more of these characteristics is sufficient for identification of probable PMR. (2) In the wake of the publication of the Bird criteria, several other criteria were developed for accurate identification of PMR at first presentation. These criteria included other features like disease duration >2 months and absence of hand swelling. (3,4,5) In sum, patients with PMR are typically over the age of 50 years old and present with discomfort they describe as pain and stiffness, often worst in the morning, that is limited to the shoulders, hip girdle, neck, and torso. (6) Because of the typically proximal nature of the discomfort, patients complain of difficulty with dressing, using a hairdryer, etc. While it’s not unusual for patients to present with some constitutional symptoms, high spiking fever is more typical of temporal arteritis than lone PMR. (4)
Rheumatoid arthritis (RA) is one of the conditions that can be confused with PMR. Pre-treatment CD8 lymphocyte levels, the presence of RF positivity, and involvement of peripheral joints are features that have been pursued as possibly useful metrics for differentiation between RA and PMR. Peripheral joint involvement is significantly more common in patients with RA, while decreased CD8 lymphocyte count is more common in patients with PMR. The presence of RF positivity, however, is not significantly more common in patients with PMR than in patients with RA. (7) Imaging is also a modality that can and should be utilized in differentiating RA from PMR. Routine x-rays of patients with PMR will usually be normal. However, MRI examination of PMR patients reveals some meaningful differences in the nature of the arthropathy present in RA versus that of PMR. The site of inflammation is largely extraarticular synovial structures in PMR; common sites of involvement include flexor, posterior tibial, and peroneal tenosynovial sheaths. In a small study comparing MRI results of PMR and RA patients, 9 of 14 patients (10/20 joints) with PMR but only 2/14 (2/20 joints) with RA had prominent edema at extracapsular sites adjacent to the joint capsule or in the soft tissues (p = 0.02). Both groups had a comparable degree of joint effusion (18 PMR, 17 RA), bursitis (18 PMR, 16 RA), and tenosynovitis (3 PMR, 2 RA). (8, 9) It is worth mentioning, however, that MRI is both expensive and not always immediately accessible. Given this reality, a more cost- and time-efficient approach to clarifying a condition that is neither clearly RA or PMR is to treat empirically with steroids, to which PMR will rapidly respond.
Proper diagnosis of PMR requires a familiarity with its signs and symptoms and a systematic approach to the diagnostic work-up that reflects an understanding of the conditions that mimic PMR. A detailed history and physical which focuses on features common to the diagnostic criteria described earlier is essential and may eliminate the need for more costly and elaborate diagnostic procedures. Any visual changes warrant prompt referral to Ophthalmology. Checking routine labs including ESR, TSH, and hepatic panel is prudent, whereas imaging should be reserved for ambiguous cases or those where empiric treatment with steroids is contraindicated.
Peer reviewed by Peter Izmirly MD, NYU Division of Rheumatology
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