Polymyalgia Rheumatica (PMR)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Polymyalgia Rheumatica (PMR) is an inflammatory disorder characterised by muscle pain and stiffness, particularly in the shoulders, neck, and hips. It primarily affects adults over the age of 50 and is often associated with giant cell arteritis (GCA).

Aetiology

The exact cause of PMR is unknown, but it is believed to result from a combination of genetic and environmental factors. Key factors include:

• Genetic predisposition, as PMR tends to run in families
• Immune system dysregulation, leading to an abnormal inflammatory response
• Infections, which may trigger or exacerbate the condition in genetically susceptible individuals

Pathophysiology

The pathophysiology of PMR involves:

• Chronic inflammation of the synovial membranes, bursae, and surrounding tissues, leading to pain and stiffness in the affected muscles
• Increased levels of pro-inflammatory cytokines, such as interleukin-6 (IL-6), which contribute to systemic inflammation
• Association with giant cell arteritis (GCA), an inflammatory condition affecting the large arteries, which can occur concurrently with PMR

Risk Factors

• Age over 50, with the highest incidence in people over 70
• Female gender, as PMR is more common in women
• European descent, particularly people of Northern European ancestry
• Family history of PMR or GCA
• Presence of autoimmune disorders, which may increase susceptibility

Signs and Symptoms

The signs and symptoms of PMR include:

• Bilateral pain and stiffness in the shoulders, neck, and hips, often worse in the morning or after periods of inactivity
• Systemic symptoms such as fatigue, malaise, low-grade fever, and weight loss
• Difficulty with daily activities, such as getting dressed or standing up from a seated position, due to muscle stiffness
• In some cases, symptoms of giant cell arteritis, such as headache, jaw claudication, or visual disturbances, may be present

Investigations

Specific investigations to diagnose PMR include:

• Blood tests: Raised inflammatory markers such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are typically elevated in PMR.
• Full blood count (FBC): To rule out other conditions, such as anaemia or infection.
• Thyroid function tests: To exclude hypothyroidism, which can mimic PMR symptoms.
• Rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies: To exclude rheumatoid arthritis.
• Imaging studies: Ultrasound or MRI may be used to assess inflammation in the joints and surrounding tissues, although these are not typically required for diagnosis.

Management

Primary Care Management

• Glucocorticoids: Low-dose prednisolone (12.5-25 mg daily) is the mainstay of treatment and typically leads to rapid symptom improvement. The dose is gradually tapered based on symptom control and inflammatory marker levels.
• Patient education: Informing patients about the chronic nature of PMR and the importance of adhering to treatment and follow-up.
• Monitoring for side effects: Regular monitoring for potential side effects of long-term glucocorticoid therapy, such as osteoporosis, diabetes, and hypertension.
• Bone protection: Calcium and vitamin D supplementation, along with bisphosphonates, may be considered to reduce the risk of glucocorticoid-induced osteoporosis.

Specialist Management

• Referral to rheumatology: For patients with atypical symptoms, suspected GCA, or those requiring high-dose glucocorticoids or immunosuppressive therapy.
• Tocilizumab: An IL-6 receptor antagonist that may be considered in patients with refractory PMR or who cannot tolerate glucocorticoids.
• Management of giant cell arteritis (GCA): Patients with GCA require urgent treatment with higher doses of glucocorticoids (40-60 mg daily) and close monitoring due to the risk of complications such as vision loss.

References

1. NHS (2024) Polymyalgia Rheumatica. Available at: https://www.nhs.uk/conditions/polymyalgia-rheumatica/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Polymyalgia Rheumatica. Available at: https://cks.nice.org.uk/topics/polymyalgia-rheumatica/ (Accessed: 24 June 2024).
3. British Medical Journal (2024) Polymyalgia Rheumatica: Clinical Features, Diagnosis, and Management. Available at: https://www.bmj.com/content/350/bmj.h2990 (Accessed: 24 June 2024).
4. American College of Rheumatology (2024) Polymyalgia Rheumatica. Available at: https://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Polymyalgia-Rheumatica (Accessed: 24 June 2024).

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