BOTTOM LINE

GCA is a large-medium vessel vasculitis affecting patients over the age of 50 (more often female) and typically over 70 years old. GCA affects the major cranial arteries (less often aorta and its appendicular branches); thus, patients commonly present with cranial claudication symptoms including new temporal headache, scalp tenderness, vision changes/blindness, and jaw claudication. Appendicular features include arm/leg claudication, decrease pulsation, and unequal blood pressures. Some develop aortic aneurysm or dissection. ESR should be elevated in virtually all patients, usually over 40-50mm/h and CRP >20mg/L. Temporal artery biopsies are helpful, specific, but insensitive; imaging modalities like Doppler ultrasound can support a GCA diagnosis if done by an experienced sonographer. Treatment requires prompt glucocorticoid (prednisone) to avoid complication of permanent vision loss, then tapered over ~52 weeks. Many patients benefit from tocilizumab for steroid sparing and decreasing flare rates; with tocilizumab, prednisone can be tapered more rapidly over 26 weeks. Relapses are common.
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EPIDEMIOLOGY

• Prevalence and incidence:
  Most common idiopathic vasculitis; crude estimates (>50 year-old population):
  • Prevalence: 500-7500/1,000,000 population
  • Annual Incidence: 80-300/1,000,000 population
• Risk
  • Age: peak incidence age 70-79 years; virtually never occurs <50 years old
  • Ethnicity: Scandinavian, northern European most common; less common Latino, Asian, Arabic, African
  • Sex: F>M, ~3:1
  • Genetic variant associations:
    • HLA region: HLA-DRB1, HLA-DQA1, HLA DQB1
    • Non-HLA region: PTPN22,  LRRC32, PLG, REL, and P4HA2

CLINICAL FEATURES

Patients present with subacute constellation of symptoms representing a systemic inflammatory process causing claudication of the major cranial arteries, aorta, and/or appendicular branches.

• SYSTEMIC
  • Fever, fatigue, weight loss. Consider GCA on differential for elderly patient with fever of unknown origin
• HEADACHE ~66%
  • Any new headache, classically temporal, but also frontal, occipital, unilateral, or generalized
  • Associated scalp tenderness (ex: scalp pain when washing/brushing hair, sleeping on pillow)
• JAW CLAUDICATION ~50%
  • Mandibular pain/fatigue onset with mastication and relieved with stopping (“jaw angina”)
  • Associated with positive temporal artery biopsy results
• OCULAR
  • Vision loss (15-20%)
    • Transient (“amaurosis fugax”) or permanent vision loss, usually monocular
    • Cause: anterior ischemic optic neuropathy (AION, 85%), central or branch retinal artery occlusion (CRAO/BRAO), posterior ischemic optic neuropathy (PION), rarely from cerebral ischemia
  • Diplopia (5%)
    • Due to ischemia of any portion oculomotor system (including brainstem)
    • More specific for GCA versus vision loss
• POLYMYALGIA RHEUMATICA, PMR (40-50%)
  • GCA with PMR = 40-50%   |   PMR patients with GCA = 10%
  • Symmetrical morning stiffness in shoulders and hip girdle sparing body distal to elbow and knees
• LARGE VESSEL (LV-GCA)
  • LV-GCA: vasculitis of aorta and “appendicular” branches, usually in the upper extremity
  • Vessels include: aorta, brachiocephalic trunk, subclavian, axillary, or femoral artery;
  • Aortic aneurysm ~10%, aortic dissection 1-6%

Patients with LV-GCA may lack cranial symptoms altogether

Compared to cranial-GCA, LV-GCA more likely: Younger, less headache, more arm claudication

• LESS COMMON
  • Stroke, TIA
  • Dementia, hallucinations
  • Non-productive cough, URTI symptoms (perhaps due to activation of cough receptors along inflamed aorta)
  • Head/neck: maxillary/dental pain, face swelling, throat pain, tongue pain/macroglossia/necrosis
• EXAM FINDINGS
  • A full cardiovascular exam is required
  • Signs of vascular compromise:
    • Unequal brachial blood pressures (>10-20mmHg difference)
    • Faint distal pulses
    • Temporal artery abnormalities (“ropey” enlargement, decreased pulsation)
    • Bruits (subclavian, axillary, carotid, abdominal)
    • Cardiac murmurs
  • Signs of PMR:
    • Symmetrical shoulder impingement/tendinitis

INVESTIGATIONS

—Bloodwork

• CBC
  • Hb: normocytic anemia due to chronic inflammation; improves with steroids
  • PTL: Thrombocytosis, reactive
  • WBC: usually normal or minimally elevated
• ESR, CRP
  • ESR and CRP are elevated; ESR usually at least >40-50mm/h
  • ESR can be affected by other variables
    • Increases ESR:
      • Age, Anemia, ESRD, paraproteinemia, Obesity, infection, cancer
    • Decreases ESR:
      • RBC-opathies (ex: sickle cell), cachexia, CHF, CLL
  • Upper limit of normal for ESR, corrected for age (roughly):
    • Men: Age/2
    • Women: (Age + 10)/2
• ALT
  • Normal, could measure baseline in case need to start tocilizumab
• SPEP
  • Elevated alpha2 fraction due to systemic inflammation, could consider testing for paraproteinemia if considering the differential for a high ESR
• Antibodies
  • No antibody associations; may have positive ANA or RF by chance

—Biopsy

• Temporal artery biopsy
  • Unilateral temporal artery biopsy at least 1cm in length; ideally within 2 weeks of starting oral glucocorticoids
  • Recommended if no access to prompt expertise in temporal artery imaging
  • Sensitivity may be as low as 40-60%; do not delay treatment of GCA to obtain biopsy if suspecting GCA
    • TAB is even less sensitive in patients with predominantly large-vessel extra-cranial GCA
  • Findings
    • Classic findings
      Transmural infiltration of lymphocytes and macrophages;  giant cells in 75% of positive biopsies
    • Less specific
      Inflammation sparing media, restricted to periadventitial small vessels and adventitial vasa vasorum
    • Non specific
      “Healed” arteritis (no inflammation but structural changes like intimal hyperplasia, fragmented internal elastic lamina, adventitial fibrosis)
    • Unlikely GCA
      Fibrinoid necrosis suggests alternative diagnosis (ex: GPA, MPA)

—Imaging

GCA is a clinical diagnosis and does not necessarily require imaging. Consider early imaging to complement the clinical assessment for diagnosing GCA, assuming high imaging expertise and prompt availability (ideally within 1 week of initiating therapy). Do not delay therapy for imaging.

Temporal artery biopsy is still a “gold standard” test for GCA diagnosis, if positive.

Cranial artery imaging

• Temporal artery ultrasound
  • May be primary imaging modality in patients with suspected cranial GCA, if imaging is desired to complement clinical assessment, bloodwork, and biopsy
  • Color Doppler Ultrasound (CDUS) should only be sought in centers with experienced sonographers
  • “Halo sign”: circumferential dark area (mural edema) around vascular lumen of temporal artery
  • “Compression sign”: persisting visibility of halo during compression
  • Sensitivity 68-88%, Specificity 77-91%
    requires skilled and experienced sonographer
    
• MRI temporal arteries
  • Limited availability, usually not first line. MRI may reveal mural inflammation
  • MR-angiography: Most MR machines (1.5-Tesla MRIs) typically lack resolution to image temporal artery
  • High-power 3-Tesla MRI, correctly protocoled, has high negative predictive value and thus may be especially helpful in patients with lower pre-test probability to rule out GCA
  • Sensitivity (Pooled) MRI: 73%; specificity: 88%
    
• CT or [18F]-Fluorodeoxyglucose (FDG) PET scanning of temporal arteries
  • CT not recommended: CT-angiography typically lacks resolution to image temporal artery. Little evidence
  • PET scan not recommended: limited by proximity of brain (cannot distinguish cranial vessels from brain)

Large vessel imaging

Image aorta and first-order branches (usually subclavian) if high clinical suspicion LV-GCA (i.e.: compatible history of extremity claudication, abnormal peripheral vascular exam, high ESR), and/or temporal artery biopsy/imaging is unrevealing

• [18F]-Fluorodeoxyglucose (FDG) PET scanning
  • PET scanning: uptake in aorta and major branches may suggest active vasculitis
  • Inexperienced readers may misinterpret atherosclerosis as LVV on PET scans
  • Sensitivity 67%–77%, Specificity 66%–100%
• MR-angiogram
  • May show circumferential vessel narrowing (“structural lesions”) and contrast enhancement of vessel wall (“active lesions” — vessel wall inflammation),
  • Vessel wall enhancement may be non-specific and can be caused by atherosclerosis
• CT
  • May show circumferential vessel narrowing
  • Sensitivity 73%, a specificity 78% (limited evidence)
• Axillary artery ultrasound
  • Ultrasound of axillary arteries may also reveal Halo Sign and Compression sign
  • Only provides incremental ~2% diagnostic sensitivity compared to Temporal Artery Ultrasound. Not routine.
  • Limited access to thoracic aorta; limited value for aortitis
• Conventional angiography
  • Not recommended, superseded by imaging modalities above.

Repeat imaging may be helpful to assess and confirm suspected flare, but is not routinely recommended for patients in clinical and biochemical remission. Serial repeat imaging could be used to follow structural damage (stenosis, occlusion, dilation, aneurysm) on a case by case basis.

Technical and Operational Parameters of Imaging Tests

(Click to Expand)

Ultrasound

• Linear probes are for supra-aortic arteries, sector or convex probes for ascending aorta and aortic arch and convex probes for abdominal aorta.
• The B-mode frequency ≥15 MHz for temporal arteries and 7–15 MHz for extracranial supra-aortic arteries. Image depth 10–20 mm for temporal arteries and 30–40 mm for extracranial supra-aortic arteries.
• Colour Doppler mode is preferred over power Doppler mode. Tissue harmonic imaging may improve delineation of the intima-media complex.
• Doppler frequencies of 7–12 MHz and 4–8 MHz should be applied for the temporal and for the extracranial supra-aortic arteries, respectively. PRF should be 2–3.5 kHz and 3–4 kHz, respectively. The angle between sound waves and artery should be ≤60°.

CT

• Collimation 0.6 mm, tube voltage 120 kV, tube current time product (mAs) determined by automatic dose modulation.
• Reconstruction slice thickness should be between 0.5 mm and 1.0 mm.
• Body-weight adapted injection of 60–120 mL of non-ionic iodinated contrast agent (≥ 350 mg/mL) using a power injector (≥ 4 mL/s).
• Arterial phase: bolus-tracking method (threshold of 100 HU); ECG triggering.
• Venous phase: 50 s after finishing the arterial phase acquisition

MRI

Cranial MRI

• 1.5 T, preferentially 3.0 T MRI scanner, minimum 8-channel head-coil.
• T1-weighted spin echo, gadolinium contrast-enhanced, fat-suppressed, high-resolution
• T2-weighted turbo spin echo (TSE), non-contrast-enhanced imaging (TR/TE 9000/143 ms) is significantly less sensitive.
• Transversal slices angulated parallel to skull base.

Body MRI

• 1.5 T, preferentially 3.0 T MRI scanner, minimum 8-channel head and neck coil and 16-channel body coil.
• MR angiography of aorta and major branches from carotid bifurcation to iliac arteries in coronal acquisition to include axillary and brachial arteries
• T1-weighted, fat-suppressed, contrast-enhanced, black blood imaging
• T2-weighted TSE imaging for edema detection in mural inflammation is less sensitive and more prone to artefacts

PET

• Hybrid PET with low-dose CT.
• Blood glucose levels: preferred <7 mmol/L, <10 mmol/L (180 mg/dL) acceptable.
• Interval between FDG infusion and image acquisition should be at least 60 min, preferably 90 min.
• Position of patient is supine, position of the arms should be arms down.
• Body parts to include: from top of head to at least midthigh, preferably to below the knees.
• Scoring FDG uptake: qualitative visual grading; if result is unclear, compare it with the liver background (grading 0–3)

DIAGNOSIS

Suspect GCA in a patient, usually Caucasian >70 years-old, with subacute claudication in the cranial arteries (new headache, scalp tenderness, vision change, jaw claudication, abnormal temporal artery) or appendicular arteries (arm/leg claudication, faint pulses, unequal blood pressures). ESR should be elevated, usually at least >40mm/h and CRP >10mg/L. Treatment with high-dose steroids should be initiated promptly if high clinical suspicion, and then temporal artery testing should be sought: usually temporal artery biopsy, but if a reliable high-quality Colour Doppler Ultrasound (CDUS) of temporal arteries is accessible, CDUS can be the first diagnostic test. Large vessel  imaging can be done based upon clinical suspicion as indicated.

—High Quality CDUS unavailable

• TAB+
  • Treat as GCA
• TAB-
  • High pre-test probability: treat as GCA if confirmatory CDUS or MR-angiography unavailable
  • Moderate pre-test probability: shared decision to treat or to monitor clinically with close serial re-assessments
  • Low-pretest probability: not GCA
    (do not pursue a TAB in the first place if low or very low pre-test probability)

—High Quality CDUS available

• CDUS positive
  • High pre-test probability: treat empirically for GCA
  • Mod/low pre-test probability: temporal artery biopsy or MR-angiography to rule in or out GCA
• CDUS negative
  • High pre-test probability: temporal artery biopsy or MR angiography rule in or out GCA
  • Low pre-test probability: not GCA

Be wary of empiric or “diagnostic trials” of prednisone: prednisone tends to improve many headache etiologies other than GCA

DIFFERENTIAL DIAGNOSIS

—Differential diagnosis Cranial GCA

• Rheumatological
  • GPA, MPA, EGPA (temporal artery and other cranial involvement of an ANCA-associated vasculitis)
  • Polyarteritis nodosa, IgG4-RD (described)
  • Juvenile temporal arteritis
• Hematological
  • Amyloidosis (amyloid deposition in temporal artery)
  • Non-Hodgkin lymphoma (intravascular lymphoma)
• Tumour
  • Local neoplasm around temporal artery
  • Metastases to skull, occipital condyle syndrome
  • Angiolymphoid hyperplasia with eosinophilia (rare benign intravascular tumour)
• Infection
  • Bacterial: bacterial sinusitis (headache, inflammation); infectious endocarditis (with septic emboli to eye)
  • Viral: varicella zoster affecting cranial arteries
  • Fungal: Aspergillus (invasive into sinuses)
  • Atypical: Syphilis (acute ischemic optic neuropathy, aortitis), nocardia (isolated ocular manifestations)
• Other
  • Migraines, Atherosclerosis, Neurosarcoid, Tolosa-Hunt, Calciphylaxis, CPPD,  Moeckenberg’s medial sclerosis

—Differential diagnosis “Halo Sign” on Temporal Artery Ultrasound

• Rheumatological
  • MPA, GPA, EGPA, PAN, juvenile temporal arteritis
• Malignant
  • Non-Hodgkin lymphoma
• Other
  • Amyloidosis, angiolymphoid hyperplasia with eosinophilia (ALHE), atherosclerosis, Migraine, infection

—Differential diagnosis Aortitis

• Rheumatological
  • Takayasu arteritis, Cogan’s, Behcets, Rheumatoid vasculitis, relapsing polychondritis, IgG4 periaortitis, sarcoid, spondyloarthropathy, relapsing polychondritis. ANCA vasculitis can affect aortic branches
• Infectious
  • Syphilis, Salmonella, Staph/strep, tuberculosis
• Metabolic
  • Atherosclerosis
• Idiopathic
  • Idiopathic retroperitoneal fibrosis
• Other
  • Non-inflammatory aortic aneurysm due to atherosclerosis (hypertension, diabetes, etc) or collagen disorders like Marfan’s and Ehlers-Danlos

CLASSIFICATION CRITERIA

Classification criteria are not meant as diagnostic criteria to diagnose disease in a single specific patient. Classification criteria are a standardized way of recruiting a well-defined homogenous population of patients in research studies in order to ensure comparability across studies of a heterogenous disease.

— ABSOLUTE REQUIREMENT

• Age ≥50 years at diagnosis

— ADDITIONAL CRITERIA

• Morning stiffness in shoulders/neck (+2)
• Sudden visual loss (+3)
• Jaw or tongue claudication (+2)
• New temporal headache (+2)
• Scalp tenderness (+2)
• Abnormal exam of temporal artery¹ (+2)

— LAB, IMAGING, BIOPSY CRITERIA

• Max ESR ≥50mm/hour or max CRP ≥10 mg/L²(+3)
• Positive temporal artery biopsy or halo sign on temporal artery ultrasound (+5)
• Bilateral axillary  involvement³ (+2)
• FDG-PT activity throughout aorta⁴ (+2)

1. Diminished pulse, tenderness, “cord-like” appearance 2. ESR, CRP measured before treatment for GCA 3. Luminal damage (stenosis, occlusion, aneurysm) on angiography (CT, MR, catheter-based), halo sign on ultrasound, PET uptake 4. Abnormal FDG uptake in arterial wall on PET scan

If the sum of scores ≥6, then classification criteria for GCA is met. Sensitivity 87.0%, Specificity 94.8%

TREATMENT

— Target

• Remission: absence of clinical signs/symptoms attributable to active GCA, normalization of inflammatory markers

— First Line

• Initiate steroid therapy promptly if mod-high suspicion of GCA without delay for biopsy/CDUS
• Initial dose
  • Prednisone 1mg/kg/day, maximum 60mg/d
  • If vision loss or critical cranial ischemia at diagnosis
    (Consider; not proven to make difference in recovery of vision loss)
    • Methylprednisolone 500-1000mg IV daily x 3 then
      prednisone 1mg/kg/d and taper as below
      
• Steroid Taper
  • Traditional Taper
    Prednisone 1mg/kg/day (up to 60mg/d) x 2-4 weeks, then
    taper 5mg weekly until 20mg/d, then
    taper 5mg every 2 weeks until 10mg/d, then
    taper daily dose by 1mg monthly until off
  • Expedited Taper (if on background tocilizumab)
    Prednisone 1mg/kg/day (up to 60mg/d) x 2-4 weeks, then
    taper 5mg weekly until 10mg/d, then
    taper 1mg weekly until 5mg/d, then
    consider tapering off completely based on disease activity

Optimal duration of glucocorticoid for GCA is not well established and should be guided by patient’s values and preferences

— Steroid sparing

Consider adding early if significant steroid side-effects, comorbidity (ex diabetes), or relapsing GCA

Some may start tocilizumab up front for all newly diagnosed GCA patients, though discussion on this topic is evolving.

• Tocilizumab
  • Tocilizumab 162mg SC weekly
  • Patients on tocilizumab may taper prednisone more quickly (as above)
  • Tocilizumab will normalize CRP (and less so, ESR) via IL-6 inhibition, which may make disease monitoring more difficult — solely on clinical assessment (and possibly serial imaging for LV-GCA)
  • Duration: unknown, at least 12-18 months
• Methotrexate
  • Methotrexate 20-25mg weekly
  • Steroid sparing benefits of Methotrexate in GCA are modest

—LV-GCA

• Generally treated the same as Cranial GCA as above
• Optimal role for repeat imaging to monitor disease is unclear; perhaps repeat CTA/MRA at 6 months then yearly if stable
• Aortic Aneurysms: if 3-5cm and enlarging with concordant ESR and/or CRPrise, consider increasing treatment
• Limb ischemia: stabilizes/improves with steroids & collateralization; revascularization surgery rare

— Monitoring Treatment Response

• Frequent assessments in early disease (ex: q1-3 months)
• Review and examine for cranial and large vessel disease activity at each visit
  • Headache, scalp tenderness, jaw claudication, limb claudication, PMR
  • Bilateral brachial blood pressures, peripheral pulses, auscultation of chest, neck, abdomen for bruits
• Review for adverse effects from steroids
  • Ex: hypertension, hyperglycemia, infection, osteoporosis
• Monitor ESR and CRP monthly; add CBC, ALT if on tocilizumab.
  • Correct upper-bound normal ESR for age and sex:
    • Men: Age/2
    • Women: (Age + 10)/2
• Imaging:
  • Could consider repeating (CT angiography, MRI) to assess structural damage in LV-GCA (stenosis, occlusion, dilatation, aneurysms). Frequency of imaging determined on case-by-case basis.

— Relapses

• Major relapse
  • Ex: new visual ischemia (diplopia, transient/permanent vision loss), limb claudication, aortitis)
  • May require increase prednisone to 1 mg/kg/day (≤60 mg/day)
• Minor relapse
  • Ex: recurrent polymyalgia rheumatica, headache, scalp tenderness
  • May only require increase to most recent asymptomatic prednisone dosage

Be wary of escalating immunosuppressive therapy based on an increase in inflammatory markers alone without compatible recurrent symptoms. May warrant more frequent clinical and/or radiographic assessments and a search for a differential underlying cause (ex: infection, malignancy)

— Adjunctive Therapy

• Aspirin 81mg/d:
  • Conflicting evidence for stroke prevention in GCA. Consider adding if other significant risk factors or if critical/flow-limiting involvement of vertebral or carotid arteries
• Osteoporosis:
  • Vitamin D, Order BMD, consider empiric bisphosphonate therapy
• Age appropriate vaccination

PROGNOSIS

• Disease course variable, 1-2 years of treatment in some, chronic steroid required in others for several years
• GCA does not adversely affect overall survival, perhaps except for patients with aortic aneurysm/dissection

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