Elliot K. Fishman M.D.
Johns Hopkins Hospital

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Vasculitis is a systemic disease characterized by non-infectious inflammation of the blood vessels. The cause can be primary (idiopathic) or secondary to an underlying disease. The precise pathophysiology of idiopathic vasculitides is unknown. Therefore, classification is based on vessel size—large, medium, small, and variable. Large vessel vasculitis (LVV) predominantly involves the large vessels (aorta and its main branches) but can also affect medium- or small-sized vessels. In variable-vessel vasculitis (VVV), any vessel can be affected, and no type of vessel predominates. 
Multimodality Imaging of Large Vessel Vasculitis
Ayaz Aghayevhttps://doi.org/10.2214/AJR.21.26150

The Revised International Chapel Hill Consensus Conference nomenclature of vasculitides was formed by experts from 12 different countries in the field of vasculitis as a proposed update to the original 1994 International Chapel Hill Consensus Conference nomenclature of vasculitides. 

large vessel vasculitis (LVV): affecting predominantly large blood vessels (aorta and its major branches)

• Takayasu arteritis (TA)
• giant cell arteritis (GCA)

medium vessel vasculitis (MVV): affecting predominantly medium blood vessels (main visceral arteries and their branches) 

• polyarteritis nodosa (PAN)
• Kawasaki disease (KD)

small vessel vasculitis (SVV): affecting predominantly small blood vessels (intraparenchymal arteries, arterioles, capillaries, and venules)

• antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)
  • microscopic polyangiitis (MPA)
  • eosinophilic granulomatosis with polyangiitis (EGPA) (formerly known as Churg-Strauss syndrome)
  • granulomatosis with polyangiitis (GPA) (formerly known as Wegener granulomatosis)
• immune complex SVV
  • anti-glomerular basement membrane (anti-GBM) disease (Goodpasture syndrome)
  • cryoglobulinaemic vasculitis (CV)
  • IgA vasculitis (IgAV) (Henoch-Schönlein purpura)
  • hypocomplementaemic urticarial vasculitis (HUV) (anti-C1q vasculitis)

variable vessel vasculitis (VVV): affecting no predominant type of vessel and can affect vessels of any size and type

• Cogan syndrome (CS)
• Behçet syndrome (BS)

single-organ vasculitis (SOV): affecting vessels of any size in only a single organ

• cutaneous leukocytoclastic angiitis
• cutaneous arteritis
• primary central nervous system vasculitis (see central nervous system vasculitides)
• isolated aortitis (see aortitis)
• others (e.g. idiopathic, pauci-immune pulmonary capillaritis)

“Multidetector CT is a useful noninvasive imaging modality for the evaluation of vasculitis and vasculitis mimics because CT can provide the information of the vessel wall change and other accompanied findings. Although CT features of various vasculitis are often overlapping, CT features via consideration of the involved vessel type, location, morphology, and associated systemic disease, can be useful in narrowing down the differential diagnosis. Getting familiar with CT features will help radiologists to establish appropriate diagnosis for vasculitis.”  
CT Features of Vasculitides Based on the 2012 International Chapel Hill Consensus Conference Revised Classification.   
Hur JH et al.
Korean J Radiol. 2017 Sep-Oct;18(5):786-798.

Diagnosis: PAN with Multiple Aneurysms in Kidney, Mesenteric Vessels

Giant cell arteritis, the most common form of vasculitis in the elderly, is characterized by granulomatous inflammation of arteries, which can lead to serious, life-threatening conditions including aortic aneurysms, ruptures, and dissections as well as blindness. Since GCA can be treated by immunosuppressant therapy, such as corticosteroids, early diagnosis and treatment may reduce the risk of serious disability and morbidity. While temporal artery biopsy is considered the gold standard to diagnosis giant cell arteritis, it is intrusive with inherent risks as well as unreliable due to tissue sampling. Imaging studies, such as computerized tomography, are nonintrusive and have been shown to identify vasculitis including giant cell arteritis.
Giant cell arteritis: A case report and review of literature
Matthew A. Crain et al.
Radiology Case Reports 16 (2021) 3734–3738

“The diagnostic criteria per American College of Rheumatology (ACR) requires at least 3 of the following: age >50 years, new onset localized headache, temporal artery tenderness or reduced pulsation, elevated erythrocyte sedimentation rate ≥50 mm/hour, and abnormal arterial biopsy (demonstrating vasculitis with predominantly mononuclear cell infiltration, granulomatous inflammation or evidence of giant cells).”
Thoracic imaging finding of rheumatic diseases. 
Gul M et al. 
J Thorac Dis. 2020;12(9):5110-5118.

“CTA can evaluate mural thickening, stenosis, and aneurysm of the aorta and branch vessels. In one study, CTA was shown to have a sensitivity of 73% and specificity of 78% to diagnose GCA. CTA has also been used in the diagnosis of TAK with high accuracy. Advantages of CT include its non-invasiveness in comparison to conventional catheter-based angiography and the ability to detect structural lesions with a higher resolution and shorter scanning time than MRA, allowing for more arterial regions to be evaluated in one session. Additionally, CTA is a preferred non-invasive imaging modality to monitor changes in aortic aneurysm morphology over time.”
“The Role of Vascular Imaging to Advance Clinical Care and Research in Large-Vessel Vasculitis.” 
Quinn, Kaitlin A, and Peter C Grayson. 
Current treatment options in rheumatology vol. 5,1 (2019): 20-35

“Large vessel vasculitis (LVV) is the most common form of primary vasculitis comprising of giant cell arteritis (GCA), Takayasu’s arteritis (TAK) and idiopathic aortitis. Early diagnosis and treatment of LVV are paramount to reduce the risk of ischemic complications such as visual loss and strokes, vascular stenosis and occlusion, and aortic aneurysm formation. Use of imaging modalities [ultrasound (US), magnetic resonance imaging (MRI), computed tomography (CT) and [18F]-fluorodeoxyglucose positron emission tomography (PET)] has steadily increased to enable assessment of cranial and extracranial arteries, as well as the aorta. These imaging modalities are less invasive, more sensitive and readily available compared to temporal artery biopsy (TAB).”
EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice summary. 
Bardi M, Diamantopoulos AP. 
Radiol Med. 2019 Oct;124(10):965-972.

Clinical differentiation between GCA and TA is sometimes difficult, but GCA predominantly affects female patients who are older than 50 years old, and is prevalent in the western countries, in contrast to TA. Pathologically, TA is commonly associated with extensive intimal and adventitial fibrosis with resultant luminal narrowing, whereas GCA is more commonly associated with extensive medial inflammation, necrosis, and formation of aortic aneurysm. “Skip lesion”, or aortic inflammation, is also more common in GCA.

Takayasu arteritis, which is also known as “aortic arch syndrome” and “pulseless disease”, is an idiopathic inflammatory disease that primarily affects large vessels such as the aorta, major branches of the aorta, and coronary and pulmonary arteries. Pathologically, TA is characterized by pan arteritis affecting all three arterial layers, and subsequent scarring of media leading to luminal occlusion

Takayasu arteritis occurs worldwide, but is much more common in Asia. Women are predominantly affected compared to men, with a 7:1 ratio . The American College of Rheumatology states that TA can be suspected when patients have at least three of the following criteria; age < 40 years at disease onset, claudication of the extremities, decreased brachial artery pressure, blood pressure difference of more than 10 mm Hg in between the arms, bruit over the subclavian arteries or aorta, and abnormal arteriographic results.

16 year old male with a history of Takayasu aortitis and severe chest pain. The CTA was ordered to rule out an aortic dissection. CTA detected no dissection but defined aneurysmal dilatation of the left main coronary artery.