Giant Cell Arteritis
An inflammatory disease of the blood vessels, often affecting the head and temples, that can cause sudden, permanent blindness if not treated immediately.
Emergency Management: Any visual disturbance in a patient suspected of GCA requires immediate IV high-dose steroids (Methylprednisolone 1g) to save the remaining vision and prevent involvement of the contralateral eye.
Giant Cell Arteritis (GCA) is a systemic immune-mediated granulomatous vasculitis that predominantly affects medium and large-sized arteries, most notably the extracranial branches of the carotid artery, particularly the temporal artery. It is the most common form of systemic vasculitis in adults.
Detailed Overview
GCA is a medical emergency because inflammation and subsequent intimal hyperplasia of the ophthalmic artery can cause sudden, irreversible, painless vision loss (anterior ischemic optic neuropathy). It almost exclusively affects individuals over the age of 50. It is highly associated with Polymyalgia Rheumatica (PMR); about half of patients with GCA have PMR. Prompt administration of high-dose corticosteroids is mandatory even before diagnostic confirmation to prevent blindness.
Epidemiology & Demographics
Exclusively occurs in adults >50 years old, peaking in the 70s. It is most common in individuals of Northern European descent (Scandinavia) and affects women 2 to 3 times more often than men.
Etiological Mechanism
The exact cause is unknown, but it is considered an autoimmune disease triggered by an unknown antigen, possibly a virus (e.g., Varicella-Zoster), in genetically susceptible individuals (HLA-DRB1*04 alleles).
Primary Causes
Autoimmune/Idiopathic
Genetic Susceptibility (HLA-DR4)
Dendritic cells in the adventitia of the vessel wall become activated and recruit CD4+ T-cells. These T-cells release interferon-gamma, which activates macrophages. Macrophages form multinucleated giant cells and release pro-inflammatory cytokines (IL-6, TNF-alpha) and metalloproteinases. This inflammatory cascade causes destruction of the internal elastic lamina. Healing responses trigger myofibroblast proliferation in the intima, causing massive intimal thickening. This narrows the arterial lumen, leading to downstream tissue ischemia (e.g., the optic nerve or masseter muscle).
Diagnostic Criteria & Guidelines
Diagnosis relies on clinical suspicion supported by markedly elevated acute phase reactants. The gold standard is a Temporal Artery Biopsy showing transmural inflammation with mononuclear cells and multinucleated giant cells. Biopsy should be at least 1-2 cm long due to 'skip lesions'. Treatment MUST NOT be delayed to wait for the biopsy.
Immediate initiation of Glucocorticoids. Without visual symptoms: Prednisone 40-60 mg PO daily. With threatened or established vision loss: Methylprednisolone 1000 mg IV daily for 3 days, then transition to oral Prednisone. Add low-dose Aspirin (81 mg) to reduce risk of ischemic events.
Second-Line & Adjunctive Therapy
Tocilizumab (IL-6 receptor antagonist) 162 mg subcutaneously weekly. Approved as a steroid-sparing agent; combining it with a 26-week prednisone taper results in higher sustained remission rates compared to steroids alone.
Surgical & Procedural Management
Temporal Artery Biopsy for diagnosis (should be performed within 1-2 weeks of starting steroids, as histopathology can remain positive for several weeks).
Patient Counseling & Advice
Warn the patient that the disease can cause sudden blindness and they must report any visual changes immediately. Explain that steroids are life-saving but will cause side effects (weight gain, mood changes, insomnia) and cannot be stopped abruptly.
Follow-Up & Monitoring Schedule
Monitor clinical symptoms and ESR/CRP every 2-4 weeks during initial steroid taper. DEXA scan at baseline to evaluate bone mineral density. Annual chest X-ray or echocardiogram/CT to screen for late complication of aortic aneurysm.
Preventive Strategies
No known prevention for the disease itself. Prevention focuses on avoiding ischemic complications through rapid diagnosis and early treatment, and preventing drug toxicity (osteoporosis prophylaxis).
Overall life expectancy is equivalent to the age-matched general population. Vision loss, if it occurs, is usually permanent. Relapses are common (up to 50%) during steroid tapering, requiring an increase in dose or addition of Tocilizumab.