Polymyalgia Rheumatica (PMR) is an inflammatory disorder that primarily affects adults over the age of 50, causing significant pain and stiffness in the muscles of the shoulders and hips. Diagnosis is complex because there is no single definitive test to confirm its presence. Instead, diagnosis relies on a combination of a patient’s symptoms, specific laboratory findings that indicate inflammation, and the methodical exclusion of other diseases that mimic the condition. The overall approach requires a clinician to integrate all this evidence, often culminating in a trial of treatment to establish the most likely cause of the patient’s discomfort.
Clinical Picture and Initial Assessment
The initial suspicion for Polymyalgia Rheumatica arises from a specific set of symptoms, which are generally rapid in onset. The hallmark presentation involves symmetrical aching and stiffness, affecting both the shoulder girdle and often the hip girdle. This discomfort is typically most noticeable in the morning, with stiffness lasting for more than 45 minutes, sometimes making it difficult to perform simple tasks like raising the arms. A thorough physical examination assesses the range of motion and locates the source of the pain, which may involve inflammation in surrounding structures, such as bursae and tendons. Physicians look for functional impairment, noting difficulty with movements like lifting the arms above the head, but true muscle weakness is not a feature of PMR.
The Role of Laboratory Testing
Once the clinical picture suggests PMR, laboratory testing checks for evidence of systemic inflammation. The two primary markers used are the Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP), which measure the body’s non-specific inflammatory response. Both are typically elevated in patients with active PMR, but they are not unique to the condition and can be raised by many other diseases. These inflammatory markers primarily support the clinical suspicion and provide a baseline for monitoring disease activity. Routine blood work is also performed, including a Complete Blood Count (CBC) and tests for liver and kidney function. These general screening tests are important for ruling out other systemic causes of the patient’s symptoms before any potential treatment is initiated.
Differential Diagnosis and Exclusion
The absence of a specific diagnostic test means that PMR diagnosis relies heavily on the process of exclusion, known as the differential diagnosis. The clinician must systematically test for and rule out other conditions that present with similar muscle pain and systemic inflammation. A significant mimic is Rheumatoid Arthritis (RA), screened for by testing specific autoantibodies like Rheumatoid Factor (RF) and anti-Cyclic Citrullinated Peptide (anti-CCP). Other conditions that must be excluded include endocrine disorders, such as hypo- or hyperthyroidism, checked via a thyroid panel, and myopathies, ruled out by testing for creatine kinase. The workup also screens for infections and for cancers that can produce paraneoplastic syndromes mimicking rheumatic diseases. Of particular importance is the exclusion of Giant Cell Arteritis (GCA), a serious condition that frequently overlaps with PMR and requires immediate, high-dose treatment. The presence of specific GCA symptoms, such as a new headache or jaw pain while chewing, necessitates urgent evaluation.
Diagnostic Confirmation Through Treatment Response
The final and most persuasive evidence in the diagnosis of Polymyalgia Rheumatica is the patient’s rapid and dramatic response to low-dose corticosteroid treatment. A trial dose of oral prednisone, typically between 12.5 and 25 milligrams daily, is administered. A significant improvement in pain and stiffness, often within 48 to 72 hours, is highly characteristic of PMR. This quick resolution confirms the diagnosis, especially after other mimicking conditions have been excluded. Conversely, a poor response should prompt the physician to reconsider the diagnosis and explore alternative causes. Diagnosis is also guided by formal classification criteria, such as those developed by the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR). These criteria combine clinical features, laboratory markers, and disease exclusion to provide a standardized framework supporting clinical judgment.