Giant cell arteritis and polymyalgia rheumatica

Giant cell arteritis (GCA) is the most common primary systemic vasculitis in adults over 50 years of age. It is a large- and medium-vessel granulomatous vasculitis predominantly affecting the branches of the external and internal carotid arteries, the aorta, and its primary branches. The feared complication is irreversible visual loss, which occurs in up to 20% of untreated patients. Polymyalgia rheumatica (PMR) is a closely related inflammatory syndrome characterised by aching and stiffness of the shoulder and pelvic girdle, occurring predominantly in individuals over 50 years. PMR and GCA frequently co-exist: approximately 40–60% of GCA patients have features of PMR, and 10–30% of PMR patients have or develop GCA. Both conditions show a strong association with HLA-DR4 and are characterised by dramatic responses to corticosteroids.

GCA and PMR share genetic susceptibility and immunopathological mechanisms, suggesting they represent a disease spectrum rather than entirely separate entities.

GCA Pathogenesis

• Dendritic cell activation in the adventitia of susceptible arteries triggers recruitment of CD4+ T cells (predominantly Th1 and Th17 subsets) and macrophages into the vessel wall
• Granuloma formation with multinucleated giant cells in the media — though giant cells are absent in up to 50% of biopsies
• Intimal hyperplasia and luminal occlusion — driven by VEGF and PDGF from activated macrophages — cause ischaemia of end-organs including the optic nerve, retina, and brain
• IL-6 is the dominant inflammatory cytokine — drives fever, elevated ESR/CRP, and anaemia of chronic disease; forms the rationale for tocilizumab
• Two phenotypes: cranial GCA (temporal artery predominant; visual loss risk) and large-vessel GCA (aorta, subclavian, axillary arteries; limb claudication, aortic aneurysm risk)

PMR Pathogenesis

• Periarticular and bursal inflammation — subacromial, subdeltoid, iliopsoas, and trochanteric bursae — accounts for the girdle pain (synovitis is minor)
• IL-6 and IL-1 predominant cytokines — explains the dramatic CRP elevation and excellent response to low-dose steroids
• No vessel wall inflammation in pure PMR — but subclinical large-vessel GCA may be present on PET imaging in some PMR patients
• HLA-DRB1*04 (HLA-DR4) is the main genetic risk factor, shared with GCA and RA

GCA and PMR are clinical diagnoses supported by laboratory and imaging findings. Presentation can be insidious over weeks or abrupt. GCA must always be considered in any patient over 50 with new headache, visual symptoms, or jaw pain.

GCA Presentations

PMR Presentation

• Bilateral shoulder girdle aching and stiffness — worse in the morning and after rest; difficulty raising arms above the head; unable to dress independently
• Hip and pelvic girdle pain — difficulty rising from a chair; thigh ache; proximal lower limb stiffness
• Morning stiffness typically >45 minutes — distinguishes inflammatory from mechanical pain
• Constitutional symptoms — fatigue, low-grade fever, weight loss, depression
• No peripheral arthritis (small joints not affected), no muscle weakness (differentiates from myopathy)
• ACR/EULAR 2012 PMR classification criteria — bilateral shoulder aching + age ≥50 + CRP/ESR elevated; also consider: hip girdle pain, absence of RF/anti-CCP, absence of other joint disease, and ultrasound bursitis

Laboratory and imaging investigations support diagnosis and exclude mimics. In suspected GCA with visual symptoms, investigations must not delay treatment — commence steroids first and investigate in parallel.

• Essential
  ESR and CRP

  ESR typically >50 mm/hr in GCA (often >100 mm/hr) and >40 mm/hr in PMR. CRP is more sensitive than ESR. Both can be normal in 4–22% of biopsy-proven GCA — do not exclude diagnosis if clinical suspicion is high.
• Essential
  FBC, UEC, LFTs

  Normocytic anaemia of chronic disease; thrombocytosis; alkaline phosphatase (ALP) elevated in 25% of GCA (hepatic artery involvement); creatinine (baseline before steroids); glucose (diabetes risk with high-dose steroids).
• Essential
  Temporal artery biopsy (TAB)

  Gold standard for GCA diagnosis. Sensitivity 50–80% (skip lesions reduce sensitivity). Perform within 2 weeks of steroid initiation — histology can remain positive for up to 4 weeks after commencing prednisolone. Request at least 1 cm segment. Bilateral TAB increases sensitivity to ~90%.
• Essential
  RF, anti-CCP, ANA

  To exclude RA and CTD as mimics of PMR. Seronegative status supports PMR diagnosis. New-onset RA in elderly can mimic PMR (but involves small joints and is RF/anti-CCP positive).
• Recommended
  Temporal artery and axillary artery ultrasound

  Non-compressible halo sign (hypoechoic oedema around vessel wall) is highly specific for GCA. Sensitivity ~80% for cranial GCA. Axillary artery involvement on ultrasound identifies large-vessel GCA. EULAR guidelines support ultrasound as first-line investigation at experienced centres.
• Recommended
  PET-CT or MRI aorta/large vessels

  PET-CT: increased FDG uptake in aorta and major branches identifies large-vessel GCA and PMR bursitis. Most sensitive before steroid commencement. MRI: aortic wall oedema/thickening in LV-GCA. Indicated if large-vessel involvement suspected or cranial GCA features absent.
• Recommended
  Shoulder and hip ultrasound (PMR)

  Subacromial/subdeltoid bursitis and bicipital tenosynovitis on ultrasound supports PMR diagnosis. Hip effusion and trochanteric bursitis also supportive. Included in ACR/EULAR 2012 PMR classification criteria as optional item.
• Recommended
  Ophthalmology assessment

  Mandatory if visual symptoms. Fundoscopy for AION (pale, oedematous optic disc); visual acuity; fluorescein angiography. Assess fellow eye urgently — sequential bilateral visual loss is a risk.

Risk stratification in GCA focuses on identifying patients at highest risk of visual loss and ischaemic complications. PMR risk stratification guides steroid dosing and duration and identifies patients likely to relapse.

Corticosteroids remain the cornerstone of treatment for both GCA and PMR. Tocilizumab has transformed GCA management, enabling steroid sparing and reducing relapse rates. All patients on long-term steroids require osteoporosis prophylaxis and cardiovascular risk management.

Directed therapy in GCA and PMR focuses on preventing and managing ischaemic complications, steroid-related complications, and disease-specific organ involvement.

Prevention of Visual Loss (GCA)

• Immediate high-dose steroids — IV methylprednisolone 500–1000 mg/day for 3 days if any visual symptoms, then oral prednisolone 1 mg/kg/day; do not wait for TAB results
• Low-dose aspirin 100 mg/day — add at diagnosis for all GCA patients; monitor for GI bleeding
• Same-day ophthalmology if visual symptoms — assess optic nerve, retina, and cranial nerve palsies; fluorescein angiography if AION suspected

Osteoporosis Prevention

• All GCA and PMR patients on prednisolone >3 months require bone protection — calcium 1000–1200 mg/day + vitamin D 800–1000 IU/day
• Bisphosphonate (alendronate 70 mg/week or risedronate 35 mg/week) — PBS-listed for corticosteroid-induced osteoporosis prevention (vertebral and hip fracture risk); commence with steroids if expected duration >3 months
• DEXA scan — at baseline and 12-monthly in patients on long-term steroids; T-score <–1.5 in patients on steroids ≥7.5 mg/day for >3 months should prompt bisphosphonate therapy

Large-Vessel GCA Surveillance

• Annual CT angiography or MRA of aorta and major branches — GCA carries 17–20× increased risk of aortic aneurysm and dissection (aortic aneurysm may present 5–10 years after initial diagnosis)
• Vascular surgery referral for aortic involvement — surveillance interval and intervention threshold determined by vessel diameter and rate of growth

Steroid Complication Management

• Diabetes risk — fasting glucose at baseline and 3–6 monthly; HbA1c annually; patient education re: steroid-induced hyperglycaemia
• PPI co-prescription — omeprazole or pantoprazole for patients on aspirin and steroids (combined GI bleeding risk)
• Blood pressure monitoring — steroids cause fluid retention and hypertension; monitor monthly during induction

Non-pharmacological management is important for minimising steroid-related morbidity, supporting functional recovery in PMR, and enabling patient self-monitoring.

Exercise and Rehabilitation

• PMR — graduated exercise programme once pain is controlled; physiotherapy for shoulder and hip girdle rehabilitation; functional strength training to counteract steroid-induced myopathy
• Weight-bearing exercise — essential for osteoporosis prevention in patients on long-term steroids

Diet and Metabolic Risk

• Low-carbohydrate, low-sodium diet — reduce steroid-induced weight gain, fluid retention, and hyperglycaemia
• Calcium-rich diet — dairy, fortified foods; supplement if dietary intake insufficient

Patient Education

• Never abruptly stop steroids — risk of adrenal insufficiency; always taper; carry steroid card
• Warning signs of GCA relapse — new headache, visual changes, jaw pain, scalp tenderness; return immediately for assessment
• Warning signs of GCA visual involvement — present to ED if sudden visual change; this is a medical emergency
• Vasculitis Australia patient support and information resources

Monitoring during treatment focuses on disease activity assessment, steroid taper guidance, and detection of steroid-related complications and disease relapse.

When to Refer Urgently

• Ophthalmology: Any new visual symptom in a patient with GCA — same-day assessment; start IV methylprednisolone before appointment if vision is acutely compromised
• Vascular surgery: Aortic aneurysm ≥5 cm; rapidly enlarging aneurysm; symptoms of aortic dissection
• Rheumatology: All new GCA; relapsing PMR requiring MTX or alternative therapy; diagnostic uncertainty; young or atypical presentations

Several patient groups with GCA or PMR require additional consideration in management.

Diabetes and Steroid-Induced Hyperglycaemia

• GCA and PMR predominantly affect elderly patients who often have pre-existing diabetes or pre-diabetes
• Steroid-induced hyperglycaemia — monitor fasting BSL weekly during high-dose induction; adjust diabetes medications accordingly
• Insulin may be required transiently during high-dose prednisolone phase; endocrinology input if difficult to control

Osteoporosis in the Elderly

• Elderly women on long-term prednisolone for GCA/PMR are at extremely high fracture risk — initiate bisphosphonate therapy concurrently with steroid commencement if expected >3 months
• Denosumab may be preferred over bisphosphonates in patients with eGFR <35; review renally dose-adjusted options

GCA Without Biopsy Confirmation

• Negative TAB does not exclude GCA — sensitivity 50–80%; treat if clinical and imaging features strongly support diagnosis
• Ultrasound halo sign or PET-CT aortic uptake can support diagnosis in TAB-negative cases with strong clinical suspicion

PMR Mimics (Differential Diagnosis)

• New-onset seronegative RA in the elderly — involves small joints; RF/anti-CCP may be positive; less dramatic steroid response
• Malignancy — paraneoplastic PMR; suspect if constitutional features disproportionate, poor steroid response, or abnormal FBC/LDH; consider CT chest/abdomen/pelvis
• Calcium pyrophosphate deposition disease — can cause acute-onset shoulder and hip pain in elderly; CPPD on joint aspiration; X-ray chondrocalcinosis
• Hypothyroidism — proximal myopathy and aching; TSH should be checked in all suspected PMR
• Statin-induced myopathy — proximal weakness and CK elevation; improves on statin cessation; CK typically normal in PMR

Stewardship in GCA and PMR focuses on appropriate steroid dosing, steroid toxicity prevention, and avoiding both under-treatment (risking visual loss) and over-treatment (cumulative steroid toxicity).

GP Role in GCA and PMR Management

• GCA — commence steroids immediately on clinical suspicion; refer urgently to rheumatology; arrange TAB within 2 weeks; low-dose aspirin; osteoporosis prophylaxis
• PMR — commence prednisolone 15–20 mg/day; confirm dramatic response (diagnostic); exclude GCA features; monitor with ESR/CRP monthly; taper gradually
• Steroid monitoring — blood pressure, glucose, weight, bone protection monthly during high-dose phase; 3-monthly when stable
• Tocilizumab — PBS criteria require rheumatologist initiation; GP can continue and monitor once established

GCA and PMR require long-term follow-up for disease activity monitoring, steroid tapering guidance, and steroid-related complication management. GCA follow-up additionally requires surveillance for aortic aneurysm and visual complications.

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