| Giant cell arteritis | |
|---|---|
| Other names | Temporal arteritis, cranial arteritis,[1] Horton disease,[2] senile arteritis,[1] granulomatous arteritis[1] |
 | |
| The arteries of the face and scalp | |
| Specialty | Rheumatology,emergency medicine,Immunology |
| Symptoms | Headache, pain over the temples,flu-like symptoms,double vision, difficulty opening the mouth[3] |
| Complications | Blindness,aortic dissection,aortic aneurysm,polymyalgia rheumatica[4] |
| Usual onset | Age greater than 50[4] |
| Causes | Inflammation of thesmall blood vessels within the walls of larger arteries[4] |
| Diagnostic method | Based on symptoms and blood tests, confirmed bybiopsy of the temporal artery[4] |
| Differential diagnosis | Takayasu arteritis,[5]stroke,primary amyloidosis[6] |
| Treatment | Steroids,bisphosphonates,proton-pump inhibitor[4] |
| Prognosis | Life expectancy (typically normal)[4] |
| Frequency | ~ 1 in 15,000 people a year (> 50 years old)[2] |
Giant cell arteritis (GCA), also calledtemporal arteritis, is aninflammatoryautoimmune disease of largeblood vessels.[4][7] Symptoms may includeheadache, pain over the temples,flu-like symptoms,double vision, and difficulty opening the mouth.[3] Complications can include blockage of theartery to the eye with resultingblindness, as well asaortic dissection, andaortic aneurysm.[4] GCA is frequently associated withpolymyalgia rheumatica.[4]
The cause is unknown.[2] The underlying mechanism involves inflammation of thesmall blood vessels that supply the walls of larger arteries.[4] This mainly affects arteries around the head and neck, though some in the chest may also be affected.[4][8] Diagnosis is suspected based on symptoms, blood tests, andmedical imaging, and confirmed bybiopsy of thetemporal artery.[4] However, in about 10% of people the temporal artery is normal.[4]
Treatment is typical with high doses ofsteroids such asprednisone orprednisolone.[4] Once symptoms have resolved, the dose is decreased by about 15% per month.[4] Once a low dose is reached, the taper is slowed further over the subsequent year.[4] Other medications that may be recommended includebisphosphonates to prevent bone loss and aproton-pump inhibitor to prevent stomach problems.[4]
It affects about 1 in 15,000 people over the age of 50 per year.[2] The condition mostly occurs in those over the age of 50, being most common among those in their 70s.[4] Females are more often affected than males.[4] Those ofnorthern European descent are more commonly affected.[5]Life expectancy is typically normal.[4] The first description of the condition occurred in 1890.[1]
Common symptoms of giant cell arteritis include:
The inflammation may affect blood supply to theeye; blurred vision or suddenblindness may occur. In 76% of cases involving the eye, theophthalmic artery is involved, causingarteritic anterior ischemic optic neuropathy.[14]
Giant cell arteritis may present with atypical or overlapping features.[15] Early and accurate diagnosis is important to prevent ischemic vision loss. Therefore, this condition is considered amedical emergency.[15]
While studies vary as to the exactrelapse rate of giant cell arteritis, relapse of this condition can occur.[16] It most often happens at low doses of prednisone (<20 mg/day), during the first year of treatment, and the most common signs of relapse are headache andpolymyalgia rheumatica.[16]
Thevaricella-zoster virus (VZV)antigen was found in 74% of temporal artery biopsies that were GCA-positive, suggesting that the VZV infection may trigger the inflammatory cascade.[17]
The disorder may co-exist (in about half of cases) withpolymyalgia rheumatica (PMR),[13] which is characterized by sudden onset of pain and stiffness in muscles (pelvis,shoulder) of the body and is seen in the elderly. GCA and PMR are so closely linked that they are often considered to be different manifestations of the same disease process. PMR usually lacks thecranial symptoms, including headache, pain in the jaw while chewing, and vision symptoms, that are present in GCA.[18]
Giant cell arteritis can affect the aorta and lead toaortic aneurysm andaortic dissection.[19] Up to 67% of people with GCA having evidence of an inflamed aorta, which can increase the risk of aortic aneurysm and dissection.[19] There are arguments for the routine screening of each person with GCA for this possible life-threatening complication by imaging the aorta. Screening should be done on a case-by-case basis based on the signs and symptoms of people with GCA.[19]
The pathological mechanism is the result of an inflammatory cascade that is triggered by an as of yet undetermined cause resulting indendritic cells in the vessel wall recruiting T cells andmacrophages to form granulomatous infiltrates.[19] These infiltrates erode the middle and inner layers of the arterialtunica media leading to conditions such as aneurysm and dissection.[19] Activation ofT helper 17 (Th17) cells involved withinterleukin (IL)6,IL-17,IL-21 andIL-23 play a critical part; specifically, Th17 activation leads to further activation of Th17 through IL-6 in a continuous, cyclic fashion.[19] This pathway is suppressed withglucocorticoids,[20] and more recently it has been found thatIL-6 inhibitors also play a suppressive role.[19]
Thegold standard for diagnosing temporal arteritis isbiopsy, which involves removing a small part of the vessel under local anesthesia and examining itmicroscopically forgiant cells infiltrating the tissue.[23] However, anegative result does not definitively rule out the diagnosis; since theblood vessels are involved in a patchy pattern, there may be unaffected areas on the vessel and the biopsy might have been taken from these parts. Unilateral biopsy of a 1.5–3 cm length is 85–90% sensitive (1 cm is the minimum).[24] Characterised as intimal hyperplasia and medial granulomatous inflammation with elastic lamina fragmentation with a CD4+ predominant T cell infiltrate, currently biopsy is only considered confirmatory for the clinical diagnosis, or one of the diagnostic criteria.[11]
Radiological examination of the temporal artery withultrasound yields ahalo sign. Contrast-enhanced brainMRI andCT are generally negative in this disorder. Recent studies have shown that 3T MRI using super high resolution imaging and contrast injection can non-invasively diagnose this disorder with high specificity and sensitivity.[25] Temporal artery thickening on imaging has been demonstrated to have highest positivelikelihood ratios for GCA when compared with other non invasive diagnostic tests.[26]
Women and men approximately 45 years old and who suffer from several complaints (at least 5 of the 16 symptoms)[27] listed below could have giant cell arteritis.
GCA is considered amedical emergency due to the potential of irreversible vision loss.[15]Corticosteroids, typically high-doseprednisone (1 mg/kg/day), should be started as soon as the diagnosis is suspected (even before the diagnosis is confirmed by biopsy) to prevent irreversible blindness secondary toophthalmic artery occlusion. Steroids do not prevent the diagnosis from later being confirmed by biopsy, although certain changes in the histology may be observed towards the end of the first week of treatment and are more difficult to identify after a couple of months.[28] The dose of corticosteroids is generally slowly tapered over 12–18 months.[22] Oral steroids are at least as effective as intravenous steroids,[29] except in the treatment of acute visual loss where intravenous steroids appear to offer significant benefit over oral steroids.[30] Short-term side effects of prednisone are uncommon but can include mood changes,avascular necrosis, and an increased risk of infection.[31] Some of the side effects associated with long-term use include weight gain,diabetes mellitus,osteoporosis, avascular necrosis,glaucoma,cataracts, cardiovascular disease, and an increased risk of infection.[32][33] It is unclear whether adding a small amount ofaspirin is beneficial or not as it has not been studied.[34] Injections oftocilizumab may also be used.[35] Tocilizumab is a humanizedantibody that targets the interleukin-6 receptor, which is a keycytokine involved in the progression of GCA.[36] Tocilizumab has been found to be effective at minimizing both recurrence, and flares of GCA when used both on its own and with corticosteroids.[36] Long term use of tocilizumab requires further investigation.[36][37] Tocilizumab may increase the risk ofgastrointestinal perforation andinfections, however it does not appear that there are more risks than using corticosteroids.[36][37]
Giant cell arteritis typically only occurs in those over the age of 50;[4] particularly those in their 70s.[22] It affects about 1 in 15,000 people over the age of 50 per year.[2] It is more common in women than in men, by a ratio of 2:1,[4] and more common in those of Northern European descent, as well as in those residing further from theEquator.[5] Roughly 1 in 5 people withpolymyalgia rheumatica also have giant cell arteritis.[38]
Giant cell arteritis and its treatment impact on people's lives because of symptoms, adverse effects of GCs and disruption to normal life.[39] People with GCA have previously ranked "losing sight in both eyes permanently", "having intense or severe pain" and "feeling weak, tired or exhausted" as important quality of life domains.[40]
The terms "giant cell arteritis" and "temporal arteritis" are sometimes used interchangeably, because of the frequent involvement of thetemporal artery. However, other large vessels such as theaorta can be involved.[41] Giant-cell arteritis is also known as "cranial arteritis" and "Horton's disease".[42] The name (giant cell arteritis) reflects the type of inflammatory cell involved.[43]