Giant Cell Arteritis
GENERAL PRINCIPLES
Epidemiology
Giant cell arteritis (GCA) is the most common systemic vasculitis in people older than 50 years. The median age of onset is 75 years, and it is four times more common in women than men.
Patients of Northern European descent are more likely to develop GCA compared to Southern European, Hispanics, and African Americans.DIAGNOSIS
Clinical Presentation
• Symptom onset tends to be gradual rather than abrupt. Patients can present with systemic, cranial, and/or large vessel manifestations. In addition, 40%-50% will have overlapping polymyalgia rheumatica (PMR) symptoms.
• Systemic symptoms include fatigue, fever, weight loss, night sweats, and generalized malaise. Cranial symptoms are various. Headache, which is typically in the temporal lobes, can also be seen over the parietal or occipital lobes. Temporal tenderness, jaw claudication (one of the most specific symptoms), and TIA or strokes which result from the involvement of internal carotid or vertebral artery. There are
also multiple different visual manifestations including:
î Amaurosis fugax: temporary vision loss due to focal ophthalmic artery lesions. Patients may also report diplopia or blurry vision.
î Anterior ischemic optic neuropathy (AION) is the most common visual manifestation in GCA. It is a permanent monocular vision loss due to lack of blood flow to the posterior ciliary artery leading to the ischemia of the optic nerve.
î Posterior ischemic optic neuropathy is uncommon; also leads to permanent monocular vision loss but it is due to the interruption of blood flow to the retrobulbar portion of the optic nerve.
î Homonymous hemianopia is rarely seen in patients with GCA; it is a consequence of the involvement of the vertebrobasilar circulation leading to occipital lobe infarction.
• Large vessel symptoms can present in combination with cranial and systemic symptoms or can be isolated.
Some symptoms include arm claudication, asymmetric pulses, paresthesias secondary to subclavian or axillary artery involvement, chest pain, aortic aneurysms, or dissection secondary to aortitis.• PMR symptoms include symmetric morning stiffness and achiness of shoulder and hip girdles, neck, and torso. Peripheral synovitis, mimicking RA or remitting seronegative symmetrical synovitis with pitting edema, can occur in some patients.
Diagnostic Testing
• Laboratories may show anemia of chronic disease, thrombocytosis, and significant elevations of ESR and CRP. A normal ESR reduces the probability of a positive temporal artery biopsy by fivefold.22
• Imaging: Different imaging modalities have been studied in GCA. These include ultrasound with Doppler, magnetic resonance angiography, and PET scan, but the best imaging method for the investigation of GCA is yet to be defined.
• Temporal artery biopsy: It is considered the gold standard for the diagnosis of GCA. The mean sensitivity for a unilateral temporal artery biopsy is 86.9%.23 Sensitivity is lower in patients with isolated large vessel involvement, in which case diagnosis is based on imaging findings. Given the segmental nature of arterial involvement by GCA, at least 2 cm should be obtained to avoid false negative result.
TREATMENT
• High-dose systemic glucocorticoids are the mainstay of therapy and should be started as soon as there is high diagnostic suspicion of GCA, especially in patients with threatened visual loss.
î Treatment should not be withheld while awaiting the performance temporal artery biopsy or imaging studies.
î Resolution of the inflammatory infiltrate of GCA occurs slowly, and histologic evidence will be evident for at least a month after glucocorticoid therapy has been instituted.
î Dose will depend on the presence or absence of visual manifestations.
î Given the prolonged course of high doses of steroids, osteoporosis prevention with calcium and vitamin D supplementation and PCP prophylaxis should be pursued in all patients.
• In patients with visual loss (or threatened) intravenous pulses of methylprednisolone are recommended. 500-1000 mg IV daily for three doses followed by oral prednisone at 1 mg/kg/d. Patients without visual loss oral steroids are recommended, prednisone 1 mg/kg (maximum 60 mg/d) or its equivalent administered daily. Taper schedule will depend on the treatment response. Dose is reduced by 10 mg every 2 weeks until 40 mg is reached. Subsequently decreased by 5 mg every 2 weeks and once 10 mg is reached, if the patient does not develop a flare, taper is usually slowed to 1 mg decrements monthly.
• Tocilizumab is the first-line steroid-sparing agent approved for GCA.24 It is an anti-IL-6 receptor monoclonal antibody; given that IL-6 plays an important role in the acute phase response, ESR and CRP measurement become unreliable to monitor disease activity.
• Methotrexate is sometimes used with moderate efficacy controlling the disease, but the three randomized controlled trials showed conflicting results.