Polymyalgia rheumatica

Polymyalgia rheumatica is a common rheumatological disorder, which is characterised by shoulder and hip girdle pain.

Polymyalgia rheumatica (PMR) is a common systemic inflammatory disease that is one of the most common indications for long-term steroids. It is characterised by myalgia and muscles stiffness with preponderance to the neck, shoulder and pelvic girdle.

Similar to giant cell arteritis (GCA), PMR is predominantly a disease of older adults and rarely presents before 50 years old. The peak prevalence is estimated between 70-80 years. Women are 2-3 times more likely to be affected than men.

The exact cause of PMR is currently unknown.

Similar to GCA, the aetiology of PMR remains unknown. There appears to be a pro-inflammatory response with elevated levels of IL-6, an increase in certain T-cell subsets and subclinical arterial inflammation in some patients.

Both genetic and environmental factors have been linked with the aetiology of PMR:

• Genetic: PMR, like GCA, has been associated with several human leucocyte antigen (HLA) alleles (e.g. HLA-DR4).
• Environmental: the cyclical pattern of cases and peak incidence in winter months suggests an infectious trigger.

Despite its name, the predominant sites of inflammation in PMR are proximal articular and periarticular structures.

The name PMR implies a myopathic process, however, the muscle in PMR is normal on histopathological assessment. The predominant site of inflammation includes bursae and tendons. Bursae are fluid-filled sacs that counteract the friction associated with tendons. Despite the site of inflammation, patients still present with generalised muscle stiffness and pain, particularly in the shoulder and pelvic girdles.

There are characteristic sites in the upper and lower extremities associated with PMR:

• Shoulder girdle: subdeltoid/subacromial bursitis and biceps tenosynovitis.
• Pelvic girdle: bursae around the greater trochanters and ischial processes. liopectineal and iliopsoas bursitis. Hamstring tendinitis and hip synovitis. 

The hallmark of PMR is symmetrical muscle aching, worse in the morning, that affects the shoulders, hips, neck and torso.

PMR should be suspected in any patient aged 50 years and older who present with two weeks of typical symptoms. 

Symptoms

• Bilateral shoulder and/or hip girdle pain
• Stiffness and upper limb tenderness: particularly mornings
• Systemic features: low-grade fever, fatigue, weight loss
• Low mood
• Peripheral symptoms: features of arthritis (predominantly knees and wrists), swelling (hands, feet, wrists, ankles) and carpel tunnel syndrome (10-15%) may be identified

Signs

• Reduced range of movement: shoulder, cervical spine, and hips 
• Inability to abduct shoulders past 90º
• Synovitis and swelling
• Motor exam: power characteristically normal. However, can be difficult to assess due to pain and stiffness that may limit examination. Chronic misuse due to pain may lead to muscle atrophy.

Giant cell arteritis

PMR is closely linked with GCA. It is estimated that 10% of patients with PMR will develop GCA. Therefore, it is essential to assess for features of GCA including unilateral headache, visual changes, jaw claudication, temporal artery tenderness, scalp pain and constitutional symptoms. 

GCA is a medical emergency because without prompt recognition and treatment it can lead to visual loss. For more information, see our notes on giant cell arteritis. 

The diagnosis of PMR is based on identifying typical clinical features and assessing response to corticosteroids.

The diagnosis of PMR should be considered if:

• Age: 50 years or older at disease onset
• Typical symptoms: bilateral, symmetrical shoulder and/or hip girdle pain associated with stiffness
• Duration: > 2 weeks and lasting > 45 minutes at a time
• Elevated inflammatory markers (ESR/CRP): supportive, but diagnosis can be made if normal
• Rapid resolution of symptoms with corticosteroids: patient-reported global improvement of 70% or more within a week

NOTE: these represent the core inclusion criteria as recommended by the British Society of Rheumatology (BSR)

Atypical features

A rheumatology referral should be considered in patients who present with atypical features:

• Younger age of onset
• Significant weight loss
• Night pain
• Neurological findings
• Absence of core symptoms
• Normal, or markedly elevated, inflammatory markers
• Chronic onset (PMR has a more acute/subacute onset)

Differential diagnosis

Due to the often vague presentation and association with constitutional symptoms, it is important to exclude an alternative diagnosis such as underlying malignancy, infection or systemic inflammatory disorders.

• Active infection: viral, infective endocarditis, tuberculosis
• Malignancy: haematological, lung, other
• Musculoskeletal disorders: frozen shoulder (bilateral adhesive capsulitis), rotator cuff injury, inflammatory arthritis, osteoarthritis, inflammatory myositis
• Endocrine disorders: thyroid or parathyroid disease
• Medications: drug-induced myalgia (e.g. statin therapy)
• Other: fibromyalgia, chronic fatigue

Giant cell arteritis

It is essential to screen for, and diagnose, GCA if present. Early diagnosis and treatment of GCA is essential to prevent long-term complications such as loss of sight (~1/5^th).

For information on the diagnosis and treatment of GCA, see our notes on giant cell arteritis. 

Investigations are useful to exclude an alternative diagnosis in patients presenting with bilateral shoulder/pelvic pain.

Usually a series of routine blood tests are enough to rule out alternative diagnoses before initiating treatment. 

More specialist tests may be needed depending on the clinical presentation. These include blood tests to screen for malignancy or inflammatory conditions and the use of imaging to exclude structural pathologies or active inflammation (i.e. synovitis).

Bloods

• FBC
• U&E
• LFT
• ESR/CRP
• Bone profile (i.e calcium)
• TFTs
• Creatine kinase (CK)
• Rheumatoid factor
• HbA1c

Specialist bloods

• Myeloma screen
• Autoimmune screen: anti-nuclear antibody, anti-cyclic citrullinated peptide antibody, complement

Imaging

• Chest x-ray
• Shoulder x-ray
• Musculoskeletal ultrasound: assess for synovitis, rotator cuff tears or joint swelling/bursitis
• MRI: specialist assessment of soft tissue structures in selected cases

Corticosteroids form the cornerstone of treatment in patients with suspected or confirmed PMR.

Corticosteroids

Following clinical assessment and routine blood tests, if PMR is felt the most likely diagnosis, patients can be started on oral prednisolone at 15 mg daily. After initiation of treatment patients should be reviewed in one week to assess the response to treatment. 

After initiation, prednisolone should be reduced once symptoms are fully controlled. This is usually after a period of 3-4 weeks. Tapering may be required over a long period (1-2 years) due to the risk of relapse on stopping too early. 

Rheumatology referral

Consider in patients with atypical symptoms, problems with steroid tapering, long-term steroid use (>2 years), recurrent flares or steroid-associated side-effects. 

Occasionally, steroid-sparing agents such as methotrexate may be used, particularly with steroid-related side-effects. However, the majority of patients should achieve disease control on low dose prednisolone. 

PMR and GCA management

In patients with PMR and suspected GCA, treatment should follow that of GCA with prompt initiation of high-dose corticosteroids to prevent complications such as sight loss. Patients should be advised about GCA symptoms and told to seek urgent medical attention if they develop.

Steroid-related complications

Steroids can be associated with numerous complications including steroid-induced hyperglycaemia, mood changes, insomnia, gastrointestinal bleeding, immunosuppression, weight gain, cushingoid appearance, osteoporosis and adrenal cortex suppression.

Patients starting steroids will usually need a long course with slow tapering over several months or years. Therefore, from the outset the following should be considered:

• Bone protection (e.g. bisphosphonates and vitamin D supplementation)
• Gastric protection (e.g. proton pump inhibitors)
• Monitoring blood sugar (at risk of steroid-induced diabetes or worsening of glycemic control in known diabetics)

In addition, patients should be given a steroid emergency card that acts as a reminder of the key side-effects and risks of steroids, including not to stop abruptly due to risk of adrenal insufficiency. 

Follow-up

Patents should be assessed after one week of treatment to assess for a response and then three-monthly within the first year. 

The majority of patients respond well to steroids and have a good longterm outcome.

Up to 45% of patients may not respond to steroids within the first 3-4 weeks of treatment and a more extended course of steroids may be needed.

Thankfully, there is no increased mortality associated with PMR, but relapse is common and patients may develop morbidity associated with side-effects from corticosteroids.