Polymyalgia Rheumatica

An inflammatory condition of the elderly characterised by bilateral aching and morning stiffness of the shoulder and pelvic girdles, with a dramatic and rapid response to low dose corticosteroids forming a central part of the diagnostic approach. It shares a close pathogenic and epidemiological relationship with giant cell arteritis, occurring in the same population and coexisting in a meaningful proportion of patients.

Pathophysiology

Inflammation centres on periarticular structures, particularly the subacromial and trochanteric bursae and the biceps tendon sheath, rather than the joints themselves, which explains the characteristic pattern of girdle pain without the synovitis typical of classical inflammatory arthritis. The underlying immune mechanism overlaps substantially with giant cell arteritis, with both conditions almost exclusively affecting patients over fifty.

Bilateral shoulder girdle pain and stiffness is the dominant feature, typically symmetrical, worse in the morning and after rest, and severe enough to interfere with dressing and other activities of daily living.

Pelvic girdle involvement (hip and thigh pain and stiffness) accompanies the shoulder symptoms in the majority, sometimes as the predominant feature.

Morning stiffness lasting forty five minutes or longer is characteristic and a useful discriminating feature from degenerative causes of girdle pain.

Constitutional symptoms (low grade fever, fatigue, weight loss) are common and, when marked, should prompt consideration of an alternative diagnosis or coexisting giant cell arteritis.

Peripheral synovitis, particularly of the wrists and knees, occurs in a minority and can cause diagnostic confusion with rheumatoid arthritis, though it is typically mild and non erosive.

Symptoms suggesting coexisting giant cell arteritis, including new headache, scalp tenderness, jaw claudication and visual disturbance, must be actively sought at every assessment given the risk of irreversible visual loss if this complication is missed.

Diagnosis is predominantly clinical, based on the characteristic symptom pattern in a patient over fifty, elevated inflammatory markers, and a rapid, often dramatic, symptomatic response to low dose corticosteroids within days, which is itself considered supportive of the diagnosis.

Erythrocyte sedimentation rate and C reactive protein are typically elevated, though a normal result does not entirely exclude the diagnosis in a small proportion of patients, and both should be checked given occasional discordance between the two markers.

Full blood count, renal and liver function, thyroid function and creatine kinase are checked to exclude alternative causes of girdle pain and stiffness, including hypothyroidism, malignancy and inflammatory myopathy (creatine kinase is normal in polymyalgia rheumatica, an important discriminator).

Rheumatoid factor and anti cyclic citrullinated peptide antibody are typically negative, helping exclude rheumatoid arthritis presenting atypically in an older patient.

Ultrasound or magnetic resonance imaging, where diagnostic uncertainty persists, may demonstrate characteristic subacromial and trochanteric bursitis, biceps tenosynovitis and glenohumeral synovitis.

Every patient must be assessed clinically for symptoms and signs of giant cell arteritis at diagnosis and at each subsequent review, given the shared population and the serious consequences of a missed diagnosis.

Low dose corticosteroids (typically prednisolone fifteen milligrams daily) are first line and produce rapid, often dramatic symptomatic improvement within days, an important diagnostic and therapeutic step, with the dose maintained until symptoms and inflammatory markers have substantially improved before a gradual taper is commenced.

The taper is prolonged, typically over one to two years, guided by symptoms and inflammatory markers rather than a fixed schedule, with relapse during tapering managed by returning to the last effective dose rather than restarting from the initial dose.

Methotrexate is considered as a steroid sparing agent for patients with relapsing disease, prolonged corticosteroid requirement, or significant corticosteroid related adverse effects.

Tocilizumab has emerging evidence and is used in some settings for relapsing or refractory disease, or where corticosteroid sparing is a particular priority.

Bone protection (calcium, vitamin D, and bisphosphonate therapy according to fracture risk assessment) is essential given the typically prolonged corticosteroid course in an older population already at elevated osteoporotic risk.

Prompt escalation to high dose corticosteroids and urgent specialist assessment is required if any symptom or sign suggestive of giant cell arteritis develops at any point during the disease course, given the risk of irreversible visual loss.

Regular review to monitor symptom control, inflammatory markers, corticosteroid related adverse effects and for emergence of giant cell arteritis, with reassessment of the diagnosis if the response to treatment is atypical or incomplete.