Diagnosis and Treatment of Giant Cell Arteritis (GCA)
Diagnostic Approach
For suspected GCA, obtain a temporal artery biopsy as the primary diagnostic test, preferably a unilateral long-segment specimen (>1 cm) performed within 2 weeks of starting glucocorticoids. 1
Initial Diagnostic Testing
Temporal artery biopsy remains the gold standard over MRI of cranial arteries, due to lack of widespread technical expertise and validation of MRI in the US. 1
Obtain a long-segment biopsy (>1 cm) rather than short-segment (<1 cm) to maximize diagnostic yield, as GCA is a focal and segmental disease. 1
Start with unilateral biopsy initially, but proceed with contralateral biopsy if the first is negative and additional evidence for cranial GCA is needed. 1
Perform biopsy within 2 weeks of starting glucocorticoids to maximize detection of histopathologic changes, though changes can be detected even later than 2 weeks. 1
If Temporal Artery Biopsy is Negative
- Obtain noninvasive vascular imaging of large vessels (MR or CT angiography of neck/chest/abdomen/pelvis, ultrasonography, or FDG-PET) with clinical assessment to aid diagnosis, as this may reveal extracranial GCA. 1
Baseline Imaging for All Newly Diagnosed Patients
- Obtain noninvasive vascular imaging to evaluate large vessel involvement at baseline, which can detect aneurysms, stenoses, and guide subsequent monitoring. 1
Treatment Approach
For Patients WITHOUT Visual Symptoms or Critical Cranial Ischemia
Initiate high-dose oral glucocorticoids (prednisone 1 mg/kg/day up to 80 mg) given daily rather than alternate-day dosing. 1
High-dose oral glucocorticoids are preferred over IV pulse glucocorticoids in patients without cranial ischemia, as routine IV pulse therapy increases infection risk that may outweigh benefits, especially in elderly patients. 1
Daily dosing is superior to alternate-day dosing for achieving higher remission rates. 1
High-dose oral glucocorticoids are preferred over moderate-dose (0.5 mg/kg/day) to achieve rapid disease control, followed by tapering over weeks to months to minimize prolonged high-dose exposure. 1
Consider adding tocilizumab (TCZ) with high-dose oral glucocorticoids as a strong recommendation for glucocorticoid-sparing effect and improved remission rates. 1
Methotrexate or glucocorticoids alone can be considered in some instances, though tocilizumab is preferred. 1
For Patients WITH Visual Symptoms, Vision Loss, or Critical Cranial Ischemia
Immediately initiate IV pulse glucocorticoids (methylprednisolone 500-1,000 mg/day for 3-5 days) followed by high-dose oral glucocorticoids, and do not delay treatment while awaiting biopsy. 2
IV pulse methylprednisolone (250-1,000 mg/day for 3 days) is recommended for threatened vision loss, as the risk of losing vision in the second eye is as high as 50% without treatment. 2
Do not delay oral glucocorticoid treatment while arranging IV therapy—start oral prednisone immediately if IV administration will be delayed. 2
Transition to high-dose oral prednisone (1 mg/kg/day, up to 60-80 mg daily) after completing IV pulse therapy. 2
Vision loss occurs in 15-35% of untreated GCA patients, primarily before therapy initiation, and visual recovery is uncommon once vision is lost. 2
Sequential bilateral blindness can occur 1-12 days after treatment initiation (median 2 days), emphasizing the critical importance of immediate aggressive treatment. 3
Glucocorticoid Tapering and Maintenance
Taper prednisone to 15-20 mg/day within 2-3 months and to ≤5 mg/day after 1 year, guided by clinical symptoms and normalization of inflammatory markers. 2
Consider adding or changing non-glucocorticoid immunosuppressive agents (methotrexate, abatacept, or tocilizumab) if patients fail to taper glucocorticoids or experience relapses. 1
Critical Pitfalls to Avoid
Never delay glucocorticoid treatment while awaiting temporal artery biopsy results, as vision loss can be permanent and irreversible. 2, 4
Do not withhold treatment based on normal inflammatory markers, as atypical presentations with low or normal ESR can occur. 4
Be aware that cumulative glucocorticoid exposure significantly increases risk of adverse events (hypertension, bone health issues, glucose intolerance), with each 1 g increase in cumulative dose increasing odds of adverse events by 6-17%. 5
Monitor closely for relapse during glucocorticoid taper using both clinical parameters and inflammatory markers, as relapses are common. 4, 6
Even with immediate IV pulse treatment, contralateral eye involvement can rarely occur up to 12 days later, though the first 2 days are most critical. 3