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Arteritis, Temporal (Giant Cell Arteritis)

Basics

  • Also called giant cell arteritis (GCA), Horton disease, cranial arteritis.
  • Inflammation of large- and medium-sized arteries, commonly cranial arteries from the aortic arch.
  • Aortic inflammation in 50% of cases.
  • New headache common (>2/3 patients).
  • Other symptoms: jaw claudication, vision loss, fatigue, fever, weight loss, polymyalgia rheumatica (PMR) symptoms, aortic arch syndrome.
  • Subacute onset typical; can be acute.
  • Medical emergency: risk of irreversible vision loss due to arteritic ischemic optic neuropathy or cerebral ischemia.

Epidemiology

  • Most common systemic vasculitis in persons ≥50 years.
  • 80% cases in 70-80 years age group.
  • Female:male ratio approx. 3:1 in Northern Europeans.
  • Incidence varies by ethnicity; US approx. 1% women, 0.5% men.
  • Prevalence in Northern Europeans: 2/1000.

Etiology and Pathophysiology

  • Unknown exact etiology; genetic predisposition, age, and ethnicity implicated.
  • Maladaptive T-cell-mediated immune response to endothelial injury.
  • Granulomatous transmural inflammation of artery wall.
  • Multinucleated giant cells found in <50% of cases.
  • Vessel stenosis from intimal hyperplasia → ischemia.
  • GCA closely linked with polymyalgia rheumatica (PMR).
  • HLA-DRB1*04 gene and polymorphisms in ICAM-1, PTPN-22 implicated.
  • Varicella zoster virus proposed as trigger but unproven.

Risk Factors

  • Age >70 years (greatest risk factor).
  • Female sex.
  • Genetic predisposition; family clustering.
  • Environmental factors.
  • Smoking history.
  • Early menopause (<43 years) and lower BMI at menopause in women 50-69 years.

Commonly Associated Conditions

  • PMR symptoms in 40-60% of GCA patients.
  • 16-21% of PMR patients have GCA.

Diagnosis

History

  • New localized headache (most common).
  • Constitutional symptoms: fever, fatigue, weight loss.
  • Visual symptoms: amaurosis fugax, diplopia, vision loss (20%, usually unilateral first).
  • Jaw claudication (strong predictor for biopsy positivity).
  • Scalp tenderness.
  • Claudication of tongue/upper extremities.
  • PMR symptoms (shoulder/hip girdle pain and stiffness).
  • Distal extremity swelling.
  • Upper respiratory symptoms.

Physical Exam

  • Temporal artery abnormalities: beading, tenderness, prominence.
  • Ill appearance.
  • Decreased peripheral pulses if large-vessel disease.
  • Fundoscopy: pale/edematous optic disc, cotton wool spots, hemorrhages.
  • Supraclavicular, axillary, supraorbital bruits.
  • Rarely involves skin, kidneys, lungs.

Differential Diagnosis

  • Migraine.
  • Herpes zoster.
  • Other vasculitis (Takayasu, Wegener, PAN).
  • Rheumatologic diseases (RA, PMR, MCTD).

Diagnostic Tests

  • American College of Rheumatology (ACR) 1990 criteria (≥3 criteria for diagnosis):
  • Age >50 years.
  • New localized headache.
  • Temporal artery abnormality.
  • ESR >50 mm/hr.
  • Positive temporal artery biopsy.
  • ESR >50 mm/hr (86% sensitivity; may be normal in some cases).
  • CRP >2.45 mg/dL more sensitive (97%).
  • Mild anemia common.
  • Color Doppler US: "halo sign" indicates vessel wall edema (operator dependent).
  • MRI/MRA helpful early (78% sensitive, 90% specific).
  • PET scan may aid difficult diagnosis.
  • Temporal artery biopsy: gold standard.
  • Specimen 7-10 mm to avoid false-negatives due to skip lesions.
  • Bilateral biopsy if initial negative but high suspicion remains.
  • Biopsy unaffected by prior glucocorticoid treatment.
  • Histology: transmural inflammation, giant cells (in <50%), disruption of internal elastic lamina.

Treatment

Medications

  • First Line:
  • High-dose prednisone 60-80 mg/day (1 mg/kg/day); do not delay treatment awaiting biopsy.
  • IV steroids if vision loss present; otherwise PO steroids equally effective.
  • Slow taper over 9-12 months; may take ≥2 years.
  • Tocilizumab (IL-6 receptor antagonist) weekly or biweekly SC may reduce relapse risk; increased infection risk.

  • Low-dose aspirin may reduce ischemic complications.

  • Second Line:

  • Methotrexate adjunct to steroids can modestly reduce relapse.
  • Cyclophosphamide, azathioprine, abatacept for refractory cases.
  • TNF inhibitors not effective as adjuncts.

Ongoing Care

  • Annual chest X-ray for aortic aneurysm surveillance.
  • Monitor for visual symptoms or relapse during steroid taper.
  • Bone protection with calcium and vitamin D due to steroids.
  • Patient education on steroid side effects, relapse signs, and photoprotection.

Prognosis

  • Variable duration: months to years.
  • Does not affect longevity unless severe aortitis occurs.
  • Vision loss usually permanent if not treated early.
  • Relapses possible; prolonged therapy sometimes necessary.

Complications

  • Vision loss.
  • Glucocorticoid-related adverse effects.

ICD10 Codes

  • M31.6 Other giant cell arteritis
  • M31.5 Giant cell arteritis with polymyalgia rheumatica

Clinical Pearls

  • Start high-dose steroids immediately if GCA suspected to prevent blindness.
  • Temporal artery biopsy is diagnostic gold standard; do not delay steroids.
  • Use slow steroid taper; monitor ESR/CRP and symptoms.
  • Bone protection and low-dose aspirin are recommended during treatment.
  • Normal ESR values: men = age/2; women = (age + 10)/2.