Polymyalgia rheumatica

Did You Know?

• The name polymyalgia comes from the Greek word Πολυμυαλγία, meaning 'pain in many muscles'.
• Scandinavians are especially vulnerable to PMR.

Signs and symptoms

Classic symptoms include moderate to severe pain and stiffness in the neck, shoulders, upper arms, thighs, and hips, which inhibits activity, especially in the morning, but usually persists to some degree throughout the day. Pain may also occur in the groin and buttocks, and can be limited to one area. Fatigue, loss of appetite possibly leading to weight loss, anemia, an overall feeling of illness or flu-like symptoms, and low-grade fever are common. High or spiking fevers may occur in patients who also have giant cell arteritis. Generalized weakness is present, but true muscle weakness suggests a different diagnosis. Inflammatory swelling of wrists or knees occurs in about 25% of cases, and pitting edema of wrists, ankles, hands, and feet in about 10%. Approximately 20% of those diagnosed also have temporal arteritis, whose symptoms include headaches, scalp tenderness, jaw or facial soreness, distorted vision, aching in the limbs from decreased blood flow, and fatigue.

Causes

The pathophysiology of polymyalgia rheumatica is not well-understood, though evidence suggests a combined genetic and environmental basis. Whether it is an autoimmune disease remains unclear, but it is at least an immune-mediated disease involving both innate and adaptive immune elements. Infectious triggers have been hypothesized in genetically susceptible people, but no specific pathogen has been proven. Proposed but unconfirmed causative agents include Mycoplasma pneumoniae, Chlamydia pneumoniae, hepatitis B virus, parvovirus B19, adenovirus, and respiratory syncytial virus. Immune cell involvement includes activation of dendritic cells and monocytes or macrophages, leading to inflammation in the synovium and bursae of the shoulder and hip girdles, primarily mediated by the innate immune system. An altered balance between Th17 and Treg cells, with increased IL-6 levels driving Th17 activation, is observed, along with disturbed B cell distribution that recovers after steroid treatment. Despite severe pain in multiple muscle groups, muscle biopsies show no localized inflammation, and electromyography is typically normal; inflammation is confined to synovial membranes and bursae. Persons with HLA-DR4 have a higher risk.

Diagnosis

No specific test exists for polymyalgia rheumatica, so diagnosis involves ruling out other causes of inflammation and pain. A doctor notes limitation in shoulder motion or swelling of wrist or hand joints. Blood tests for erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are commonly performed; elevated levels suggest inflammation but are not specific to PMR. Because PMR is sometimes associated with temporal arteritis, which requires more aggressive therapy, a biopsy of the temporal artery may be taken to test for that condition.

Treatment

Prednisone is the usual drug for PMR, with treatment often lasting more than a year. If a patient does not experience dramatic improvement after three days of 10–20 mg oral prednisone per day, the diagnosis should be reconsidered; relief can sometimes occur within hours. Nonsteroidal anti-inflammatory drugs such as ibuprofen are ineffective for initial treatment but may be used alongside a maintenance corticosteroid dose. Patients are encouraged to exercise and eat a diet of fruits, vegetables, whole grains, and low-fat meat and dairy, avoiding refined sugars and salt. Research in the UK suggests a falls assessment at diagnosis and regular treatment reviews are beneficial.