Polymyalgia rheumatica

Polymyalgia rheumatica (PMR) is a common inflammatory disease that predominantly affects individuals > 50 years of age and occurs more often in women than men. Patients typically present with acute pain and stiffness in the shoulder girdle, pelvic girdle, and/or neck, and constitutional symptoms. Diagnosis is clinical. Findings from laboratory studies (i.e., elevated inflammatory markers, negative creatine kinase, and absence of autoantibodies) and imaging such as ultrasound further support the diagnosis. Oral glucocorticoids are the mainstay of treatment. All patients should be monitored for features of giant cell arteritis (GCA), which is commonly associated with PMR.

• Sex: ♀ > ♂ (3:1) ^[1]
• Age of onset: > 70 years (very rare in individuals < 50 years) ^[2][3][4]
• More common in individuals of Northern European descent ^[5]

Epidemiological data refers to the US, unless otherwise specified.

• Unknown
• Possible contributing factors are:
  • Genetic predisposition (e.g., human leukocyte antigen HLA-DR4)
  • Association with GCA: Approx. 20% of individuals with PMR also have GCA. ^[3][4]

• Systemic features ^[3][4]
  • Constitutional symptoms: fever, weight loss, night sweats
  • Fatigue and malaise
  • Depressed mood
  • Symptoms of anemia
• Musculoskeletal features: shoulder girdle, neck, and pelvic girdle ^[3][4]
  • Pain: acute onset, bilateral usually, worse at night
  • Morning stiffness (> 45 minutes) ^[4]
  • Muscular atrophy and weakness: not directly caused by PMR but resulting from reduced activity due to pain and stiffness
• Features of GCA: GCA and PMR share clinical features and may occur simultaneously.

General principles ^[3][6]

• PMR is a clinical diagnosis.
• The 2012 EULAR/ACR classification criteria for PMR help to distinguish it from other inflammatory conditions but are not diagnostic. ^[7]
• Laboratory studies help to exclude alternative diagnoses.
• Imaging studies (e.g., ultrasound) may be requested in consultation with specialists to support the diagnosis.
• Refer patients with atypical clinical presentations (e.g., peripheral arthritis, age < 60 years) to rheumatology.
• A rapid response (< 7 days) to low to medium doses of glucocorticoids helps confirm the diagnosis.

All patients should be examined for features of GCA.

Laboratory studies ^[3][4]

• CBC: thrombocytosis, normocytic anemia
• Inflammatory markers: ↑ ESR; and/or ↑ CRP; normal levels of both suggest a different diagnosis.
• Serology: absent autoantibodies (including rheumatoid factor)
• Muscle enzymes: normal levels of creatine kinase and other enzymes

Normal creatine kinase levels and the absence of autoantibodies help differentiate PMR from other rheumatic diseases (e.g., polymyositis, dermatomyositis, rheumatoid arthritis).

Imaging ^[4][8]

• Ultrasound (e.g., shoulder and/or hip)
  • Indications: to help support the diagnosis (not routinely required)
  • Findings (often bilateral)
    • Subdeltoid bursitis
    • Biceps tenosynovitis
    • Trochanteric bursitis, glenohumeral synovitis, and hip synovitis (less common)
• 18F-FDG PET-CT scan: considered in atypical presentations to rule out alternative diagnoses (e.g., GCA, malignancy)

• Giant cell arteritis
• Rheumatoid arthritis
• Polymyositis and dermatomyositis
• Fibromyalgia
• Paraneoplastic syndromes associated with lung cancer, e.g., Stiff person syndrome
• Thyroid disorders
• Statin-induced myopathy
• Rotator cuff disease

The differential diagnoses listed here are not exhaustive.

Patients at high risk for side effects of glucocorticoid therapy, relapse, or prolonged therapy should be referred to rheumatology.

Pharmacological treatment ^[3][4][6]

• Glucocorticoids (low to medium dose)
  • Indicated for all patients with PMR
  • Oral prednisone or IM methylprednisolone (off-label) ^[6]
  • Dose adjustment is based on treatment response. ^[6]
• Other immunosuppressive agents
  • Methotrexate: may be used as a glucocorticoid-sparing agent
  • Sarilumab: may be used in patients with relapse during tapering of glucocorticoids ^[9]

Glucocorticoids typically provide rapid symptomatic relief for PMR.

Supportive care ^[4][6]

Patients with PMR are almost exclusively older adults, with an increased prevalence of comorbidities and risk of complications.

• Refer patients to physiotherapy for a tailored program to maintain muscle mass and function.
• Counsel patients on preventing complications, e.g.:
  • ASCVD prevention
  • Recommended vaccines
  • Side effects of glucocorticoid therapy

• Most patients adequately respond to glucocorticoid therapy.
• Relapses occur in up to 50% of patients. ^[4]
• Up to 20% of patients have concomitant GCA. ^[3][4]
• Factors associated with a worse prognosis ^[4]
  • Female sex
  • High ESR at time of diagnosis
  • High doses of glucocorticoids