Arthritis - polymyalgia rheumatica
Description
- Inflammatory syndrome of bilateral shoulder and hip girdle pain and stiffness in people over 50
- Subacute onset over days-weeks; "I went to bed well and woke up 90 years old"
- Morning stiffness >45-60 min; cannot roll over in bed, lift arms to comb hair, or rise from a chair
- Pain is proximal and symmetrical; weakness is apparent, not real - power is normal when pain is overcome
- Systemic features in ~1/3: low-grade fever, weight loss, fatigue, malaise, depression
- Peripheral features in up to half - asymmetrical oligoarthritis (knee, wrist), carpal tunnel, distal extremity swelling with pitting oedema
- Bursitis and tenosynovitis, not myositis, is the pathology - CK is normal
The inseparable relationship with giant cell arteritis
- ~15-20% of PMR develops GCA; ~40-50% of GCA has PMR symptoms
- *Ask every PMR patient about GCA symptoms at every visit, and warn them to present immediately*
Epidemiology
- Virtually never under 50 - a "PMR" diagnosis under 50 is wrong until proven otherwise
- Peak incidence 70-80 yr; incidence ~50-100 per 100,000 per year over 50
- F>M ~2-3:1
- Strong northern European ancestry gradient; uncommon in Asian and African populations
- The second commonest indication for long-term glucocorticoids in the community after asthma/COPD
Aetiopathogenesis
- Unknown trigger in a genetically susceptible host; *HLA-DRB104** association (shared with GCA and RA)
- IL-6 is central - drives the systemic response, the ESR/CRP rise, and the therapeutic rationale for IL-6 receptor blockade
- Pathology is periarticular: subacromial/subdeltoid bursitis, biceps tenosynovitis, glenohumeral synovitis, trochanteric bursitis, interspinous bursitis
- *Muscle is histologically normal - PMR is not a myopathy*
- Environmental/infective triggers proposed but unproven; seasonal and cyclical incidence peaks
- Ageing immune system: inflammageing, reduced T-cell repertoire
Diagnosis
A clinical diagnosis of exclusion supported by inflammatory markers and a steroid response.
Core requirements
- Age >=50 + bilateral shoulder (+/- hip) girdle pain + morning stiffness >45 min + raised ESR and/or CRP
EULAR/ACR classification criteria (score, requires the core requirements above)
| Feature | Points |
|---|---|
| Morning stiffness >45 min | 2 |
| Hip pain or limited range of movement | 1 |
| Absence of RF and anti-CCP | 2 |
| Absence of other joint involvement | 1 |
| (With ultrasound) bilateral subdeltoid bursitis/biceps tenosynovitis/glenohumeral synovitis | 1 |
| (With ultrasound) additional shoulder + hip findings | 1 |
- >=4 without ultrasound, or >=5 with ultrasound
Investigations
- ESR and CRP - raised in ~90%
- *Up to 7-20% have normal inflammatory markers - a normal ESR does not exclude PMR in a typical clinical picture*
- Normal CK - a raised CK means myositis, hypothyroidism or a statin, not PMR
- RF and anti-CCP negative (positive -> elderly-onset RA)
- FBE (normochromic anaemia, thrombocytosis), UEC, LFT (ALP may be raised), TSH, calcium, protein electrophoresis, vitamin D
- Urinalysis, CXR - screening for occult malignancy and infection
- Ultrasound of shoulders and hips: bursitis/tenosynovitis - also excludes rotator cuff tear
- PET-CT where the diagnosis is uncertain or large-vessel vasculitis is suspected
- Baseline before steroids: BP, glucose/HbA1c, DEXA, weight, cataract/glaucoma history
Differential - what PMR is confused with
| Discriminator | |
|---|---|
| Elderly-onset RA | Small joint synovitis, RF/CCP positive, erosions, less complete steroid response |
| Giant cell arteritis | Headache, jaw claudication, visual symptoms, scalp tenderness |
| Myositis | True weakness, raised CK |
| Hypothyroidism | TSH; myalgia and raised CK |
| Statin myopathy | Temporal relation to the drug; CK |
| Malignancy (myeloma, lymphoma, solid tumour) | Weight loss, paraprotein, poor steroid response |
| Infection - endocarditis, osteomyelitis, TB | Fever pattern, murmur, cultures |
| Bilateral rotator cuff disease / adhesive capsulitis | Normal inflammatory markers, restricted passive range |
| Parkinson disease, hypovitaminosis D, fibromyalgia, OSA | No inflammatory response |
- *The dramatic steroid response is a diagnostic criterion in practice - failure to improve substantially within a week of adequate prednisolone should make you doubt the diagnosis and re-investigate*
Management
A. Glucocorticoids - still the first-line treatment
- Prednisolone 12.5-25 mg daily; 15 mg is the usual starting dose
- Higher end if heavy, severe symptoms or high relapse risk; lower end if diabetic, osteoporotic or frail
- Expect a >70% symptom improvement within 1 week and normalisation of inflammatory markers within 4 weeks
- *Do NOT start steroids before taking bloods - and never* give steroids for possible PMR without first excluding GCA and considering infection and malignancy
- If GCA is suspected, the dose is completely different: prednisolone 40-60 mg daily, or IV methylprednisolone if visual symptoms - do not wait for biopsy
B. Tapering - the real skill
- Taper to 10 mg/day over ~4-8 weeks, then reduce by ~1 mg every 4 weeks
- Typical total treatment duration 1-3 years; ~1/3 need longer
- Taper against symptoms and function, not against the ESR alone - a rising ESR in a well patient is not a relapse
- Relapse: return to the previous effective dose (usually the last dose at which the patient was well), then taper more slowly
- Relapse occurs in ~50%, most often in the first year and at doses below 10 mg
C. Steroid-sparing therapy - when to escalate
- Indications: relapsing disease, inability to taper below ~7.5-10 mg, or a patient at high risk from steroids (diabetes, osteoporosis, glaucoma, obesity, psychiatric illness)
- Methotrexate - the conventional first choice, modest evidence, cheap and available
- IL-6 receptor blockade is the class change
- Sarilumab 200 mg SC fortnightly has phase 3 evidence in relapsing PMR with a rapid (14-week) prednisone taper
- Tocilizumab improves glucocorticoid-free remission and cumulative steroid exposure in new-onset and relapsing disease
- Australian availability for PMR is limited and largely not PBS-subsidised - specialist decision
- Caution: IL-6 blockade abolishes CRP and ESR, masks infection, and carries a risk of GI perforation and diverticulitis
- Leflunomide has supportive evidence; JAK inhibitors are under study
D. Manage the steroid, not just the disease - this is where the geriatric marks are
- Bone: calcium and vitamin D for all; bisphosphonate if the expected duration is >=3 months at >=5-7.5 mg/day, or if there is prior fracture or a low DEXA T-score
- Glucose: check HbA1c/BSL at baseline and after 4 weeks - steroid-induced diabetes is common and post-prandial; a normal fasting glucose does not exclude it
- Blood pressure and weight
- PPI if also on NSAIDs or with peptic ulcer history
- Falls, myopathy, skin fragility, cataract and glaucoma, mood disturbance and insomnia
- Infection: vaccinate (influenza, COVID, pneumococcal, shingles - live zoster vaccine only before or at low steroid doses; Shingrix is preferred and non-live); consider PJP prophylaxis only at high doses with additional immunosuppression
- Steroid card, sick-day rules and adrenal insufficiency counselling - do not stop abruptly after prolonged therapy; consider a morning cortisol when tapering below 5 mg
- Physiotherapy and graded exercise to preserve function and muscle
E. Vigilance for GCA
- Educate every patient: new headache, scalp tenderness, jaw claudication, visual blurring or amaurosis = same-day presentation
- New symptoms -> high-dose steroid immediately, then temporal artery ultrasound/biopsy or large-vessel imaging
Associations
- Giant cell arteritis - the dominant association in both directions
- Large-vessel vasculitis (aortitis, subclavian) - suspect if fever, weight loss, limb claudication or refractory disease
- Elderly-onset RA and late-onset spondyloarthropathy
- Distal extremity swelling with pitting oedema; carpal tunnel syndrome
- Depression and sleep disturbance
- Glucocorticoid complications - osteoporosis and fracture, diabetes, hypertension, cataract, infection, skin thinning, adrenal suppression, proximal myopathy
- Higher rates of thoracic aortic aneurysm in long-term follow-up
Natural history & complications
- Self-limiting in most: median treatment duration ~1-3 yr; ~1/3 need steroids beyond 2 years
- ~50% relapse at least once, typically at doses below 10 mg or during rapid tapering
- Mortality is not increased by PMR itself - the morbidity comes from cumulative glucocorticoid exposure
- Mean cumulative prednisolone exposure is often >5 g - plan for bone protection and glucose monitoring from day one
- Reconsider the diagnosis if: incomplete response to adequate steroids, need for >10 mg beyond 6 months, atypical features, or new red flags -> re-investigate for malignancy, infection, elderly-onset RA or large-vessel vasculitis
- Screen for GCA at every review; ~15-20% cumulative incidence
Monitor
- Symptoms, morning stiffness, function, steroid dose and cumulative exposure
- ESR/CRP at each taper step (but treat the patient, not the number)
- BP, weight, HbA1c/glucose, DEXA every 1-2 yr, eyes
- GCA symptom review
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