Although the cause of Takayasu arteritis is unknown, the condition is characterized by segmental and patchy granulomatous inflammation of the aorta and its major derivative branches. This inflammation leads to arterial stenosis, thrombosis, and aneurysms. There is irregular fibrosis of the blood vessels due to chronic vasculitis, leading to sometimes massive intimal fibrosis (fibrosis of the inner section of the blood vessels). Prominent narrowing due to inflammation, granuloma, and fibrosis is often seen in arterial studies such as magnetic resonance angiography (MRA), computed tomography angiography (CTA), or arterial angiography (DSA).

This type of arteritis is most common in females, with a median age of 25 years. Takayasu arteritis is more common in women of Asian descent who are in their reproductive years. However, over the past decades, its incidence in Africa, Europe, and North America has been increasing. Takayasu arteritis is an inflammatory disease that mainly affects the larger vessels such as the aorta and its surrounding branches. Research focused on Takayasu arteritis in the western parts of the world remains limited. An estimation suggests that, each year, the number of cases per million people is 2.6.

The genetic contribution to the pathogenesis of Takayasu's arteritis is supported by the genetic association with HLA-B∗52. A 2013 large collaborative study uncovered multiple additional susceptibility loci for this disease, increasing its number of genetic loci to five risk loci across the genome. About 200,000 genetic variants were genotyped in two ethnically divergent Takayasu's arteritis cohorts from Turkey and North America by using a custom-designed genotyping platform (Immunochip). Additional genetic variants and the classical HLA alleles were imputed and analyzed. The study identified and confirmed two independent susceptibility loci within the HLA region (r2 < 0.2): HLA-B/MICA (rs12524487, OR = 3.29, p = 5.57 × 10-16) and HLA-DQB1/HLA-DRB1 (rs113452171, OR = 2.34, p = 3.74 × 10-9; and rs189754752, OR = 2.47, p = 4.22 × 10-9). In addition, a genetic association was identified and confirmed between Takayasu's arteritis and the FCGR2A/FCGR3A locus on chromosome 1 (rs10919543, OR = 1.81, p = 5.89 × 10-12). The risk allele at this locus results in increased mRNA expression of FCGR2A. In addition, a genetic association between IL12B and Takayasu arteritis was established (rs56167332, OR = 1.54, p = 2.18 × 10-8). A fifth genetic locus for the disease in an intergenic region on chromosome 21q22 downstream of PSMG1 was revealed (P=4.39X10-7). A recent genome-wide association study (GWAS) identified genetic susceptibility loci for Takayasu arteritis with a genome-wide level of significance in IL6 (rs2069837) (odds ratio [OR] 2.07, P = 6.70 × 10(-9)), RPS9/LILRB3 (rs11666543) (OR 1.65, P = 2.34 × 10(-8)), and the intergenic locus on chromosome 21q22 (rs2836878) (OR 1.79, P = 3.62 × 10(-10)). The genetic susceptibility locus in RPS9/LILRB3 lies within the leukocyte receptor complex gene cluster on chromosome 19q13.4, and the disease risk variant in this locus correlates with reduced expression of multiple genes including the inhibitory leukocyte immunoglobulin-like receptor gene LILRB3 (P = 2.29 × 10(-8)). In addition, this study identified additional candidate susceptibility genes with suggestive levels of association (P < 1 × 10(-5)) including PCSK5, LILRA3, PPM1G/NRBP1, and PTK2B.

Arteritis is the inflammation of the walls of arteries, usually as a result of infection or autoimmune response. Arteritis, a complex disorder, is still not entirely understood. Arteritis may be distinguished by its different types, based on the organ systems affected by the disease. A complication of arteritis is thrombosis, which can be fatal. Arteritis and phlebitis are forms of vasculitis.

Giant-cell arteritis (GCA), also called temporal arteritis, is an inflammatory disease of blood vessels. Symptoms may include headache, pain over the temples, flu-like symptoms, double vision, and difficulty opening the mouth. Complication can include blockage of the artery to the eye with resulting blindness, aortic dissection, and aortic aneurysm. GCA is frequently associated with polymyalgia rheumatica.

The cause is unknown. The underlying mechanism involves inflammation of the small blood vessels that occur within the walls of larger arteries. This mainly affects arteries around the head and neck, though some in the chest may also be affected. Diagnosis is suspected based on symptoms, blood tests, and medical imaging, and confirmed by biopsy of the temporal artery. However, in about 10% of people the temporal artery is normal.

Treatment is typically with high doses of steroids, such as prednisone. Once symptoms have resolved the dose is then decreased by about 15% per month. Once a low dose is reached, the taper is slowed further over the subsequent year. Other medications that may be recommended include bisphosphonates to prevent bone loss and a proton pump inhibitor to prevent stomach problems.

It affects about 1 in 15,000 people over the age of 50 a year. The condition typically only occurs in those over the age of 50 being most common among those in their 70s. Females are more often affected than males. Those of northern European descent are more commonly affected. Life expectancy is typically normal. The first description of the condition occurred in 1890.

The varicella-zoster virus antigen was found in 74% of temporal artery biopsies that were GCA-positive, suggesting that the VZV infection may trigger the inflammatory cascade.

The disorder may coexist (in a half of cases) with polymyalgia rheumatica (PMR), 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. Other diseases associated with temporal arteritis are systemic lupus erythematosus, rheumatoid arthritis, and severe infections.

Giant-cell arteritis can involve branches of the aorta as well, leading to an aortic aneurysm or dissection. For this reason, patients should be followed with serial chest X-rays.

Treatment of aortitis depends on the underlying cause. Infectious causes commonly require antibiotic treatment, while those associated with autoimmune vasculitides are generally treated with steroids.

Management includes the following treatment priorities: stop the inflammation, treat complications, prevent and monitor for re-occurrence.

If untreated, has three distinct phases. The first is a prepulseless inflammatory stage with nonspecific symptoms such as fatigue, arthralgias, and low-grade fevers. Phase two includes vascular inflammation with pain secondary to the condition, along with tenderness to palpation over the site. The last phase includes symptoms of ischemia and pain associated with the use of limbs. Limbs are also cool and clammy in this stage.

Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis. Vasculitis is primarily caused by leukocyte migration and resultant damage.

Although both occur in vasculitis, inflammation of veins (phlebitis) or arteries (arteritis) are their own are separate entities.

Vasculitis secondary to connective tissue disorders. Usually secondary to systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), relapsing polychondritis, Behçet's disease, and other connective tissue disorders.

Vasculitis secondary to viral infection. Usually due to hepatitis B and C, HIV, cytomegalovirus, Epstein-Barr virus, and Parvo B19 virus.

Inflammatory involvement of tertiary syphilis begins at the adventitia of the aortic arch which progressively causes obliterative endarteritis of the vasa vasorum. This leads to narrowing of the lumen of the vasa vasorum, causing ischemic injury of the medial aortic arch and then finally loss of elastic support and dilation of the vessel. Dissection of the aortic arch is rare due to medial scarring. As a result of this advanced disease process, standard methods of angiography/angioplasty may be impossible for those with suspected coronary heart disease. However, these patients may be candidates for diagnostic CT as a less invasive modality. This disorder is also known eponymously as Heller-Döhle syndrome.

Necrotizing vasculitis also called Systemic necrotizing vasculitus (SNV) is a category of vasculitis, comprising vasculitides that present with necrosis.

Examples include giant cell arteritis, microscopic polyangiitis, and granulomatosis with polyangiitis.

ICD-10 uses the variant "necrotizing vasculopathy". ICD-9, while classifying these conditions together, doesn't use a dedicated phrase, instead calling them "polyarteritis nodosa and allied conditions".

When using the influential classification known as the "Chapel Hill Consensus Conference", the terms "systemic vasculitis" or "primary systemic vasculitides" are commonly used. Although the word "necrotizing" is omitted, the conditions described are largely the same.

Obliterating endarteritis also called "obliterating arteritis" is severe proliferating endarteritis (inflammation of the intima or inner lining of an artery) that results in an occlusion of the lumen of the artery. Obliterating endarteritis can occur due to a variety of medical conditions such as a complication of radiation poisoning, tuberculosis meningitis or a syphilis infection.

Vasculitis can be classified by the cause, the location, the type of vessel or the size of vessel.

- "Underlying cause". For example, the cause of syphilitic aortitis is infectious (aortitis simply refers to inflammation of the aorta, which is an artery.) However, the causes of many forms of vasculitis are poorly understood. There is usually an immune component, but the trigger is often not identified. In these cases, the antibody found is sometimes used in classification, as in ANCA-associated vasculitides.

- "Location of the affected vessels". For example, ICD-10 classifies "vasculitis limited to skin" with skin conditions (under "L"), and "necrotizing vasculopathies" (corresponding to systemic vasculitis) with musculoskeletal system and connective tissue conditions (under "M"). Arteritis/phlebitis on their own are classified with circulatory conditions (under "I").

- "Type or size of the blood vessels" that they predominantly affect. Apart from the arteritis/phlebitis distinction mentioned above, vasculitis is often classified by the caliber of the vessel affected. However, there can be some variation in the size of the vessels affected.

According to the size of the vessel affected, vasculitis can be classified into:

- Large vessel: Polymyalgia rheumatica, Takayasu's arteritis, Temporal arteritis

- Medium vessel: Buerger's disease, Kawasaki disease, Polyarteritis nodosa

- Small vessel: Behçet's syndrome, Eosinophilic granulomatosis with polyangiitis, Cutaneous vasculitis, Henoch–Schönlein purpura, Microscopic polyannulomatosis ConditionofSome disorders have vasculitis as their main feature. The major types are given in the table below:

Takayasu's arteritis, polyarteritis nodosa and giant cell arteritis mainly involve arteries and are thus sometimes classed specifically under arteritis.

Furthermore, there are many conditions that have vasculitis as an accompanying or atypical feature, including:

- Rheumatic diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and dermatomyositis

- Cancer, such as lymphomas

- Infections, such as hepatitis C

- Exposure to chemicals and drugs, such as amphetamines, cocaine, and anthrax vaccines which contain the Anthrax Protective Antigen as the primary ingredient.

In pediatric patients varicella inflammation may be followed by vasculitis of intracranial vessels. This condition is called post varicella angiopathy and this may be responsible for arterial ischaemic strokes in children.

Several of these vasculitides are associated with antineutrophil cytoplasmic antibodies. These are:

- Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis)

- Eosinophilic granulomatosis with polyangiitis (formerly known as Churg-Strauss syndrome)

- Microscopic polyangiitis

No circumstances are certain as to which an individual will get polymyalgia rheumatica, but a few factors show a relationship with the disorder.

- Usually, PMR only affects adults over the age of 50.

- The average age of a person who has PMR is about 70 years old.

- Women are twice as likely to get PMR as men.

- Caucasians are more likely to get this disease. It is more likely to affect people of Northern European origin; Scandinavians are especially vulnerable.

- About 50% of people with temporal arteritis also have polymyalgia rheumatica.

Syphilitic aortitis (SA) is inflammation of the aorta associated with the tertiary stage of syphilis infection. SA begins as inflammation of the outermost layer of the blood vessel, including the blood vessels that supply the aorta itself with blood, the vasa vasorum. As SA worsens, the vasa vasorum undergo hyperplastic thickening of their walls thereby restricting blood flow and causing ischemia of the outer two-thirds of the aortic wall. Starved for oxygen and nutrients, elastic fibers become patchy and smooth muscle cells die. If the disease progresses, syphilitic aortitis leads to an aortic aneurysm. Unlike atherosclerosis, which typically manifests in older people, syphilitic aortitis typically affects those under the age of 50. It has become rare in the developed world with the advent of penicillin treatments after World War II.

Ostial disease, namely coronary ostial stenosis, is the occlusion of coronary ostium. Causing factors include atherosclerosis, syphilis, Kawasaki disease, and Takayasu's arteritis, etc.

With respect to embolic and hemodynamic causes, this transient monocular visual loss ultimately occurs due to a temporary reduction in retinal artery, ophthalmic artery, or ciliary artery blood flow, leading to a decrease in retinal circulation which, in turn, causes retinal hypoxia. While, most commonly, emboli causing amaurosis fugax are described as coming from an atherosclerotic carotid artery, any emboli arising from vasculature preceding the retinal artery, ophthalmic artery, or ciliary arteries may cause this transient monocular blindness.

- Atherosclerotic carotid artery: Amaurosis fugax may present as a type of transient ischemic attack (TIA), during which an embolus unilaterally obstructs the lumen of the retinal artery or ophthalmic artery, causing a decrease in blood flow to the ipsilateral retina. The most common source of these athero-emboli is an atherosclerotic carotid artery. However, a severely atherosclerotic carotid artery may also cause amaurosis fugax due to its stenosis of blood flow, leading to ischemia when the retina is exposed to bright light. "Unilateral visual loss in bright light may indicate ipsilateral carotid artery occlusive disease and may reflect the inability of borderline circulation to sustain the increased retinal metabolic activity associated with exposure to bright light."

- Atherosclerotic ophthalmic artery: Will present similarly to an atherosclerotic internal carotid artery.

- Cardiac emboli: Thrombotic emboli arising from the heart may also cause luminal obstruction of the retinal, ophthalmic, and/or ciliary arteries, causing decreased blood flow to the ipsilateral retina; examples being those arising due to (1) atrial fibrillation, (2) valvular abnormalities including post-rheumatic valvular disease, mitral valve prolapse, and a bicuspid aortic valve, and (3) atrial myxomas.

- Temporary vasospasm leading to decreased blood flow can be a cause of amaurosis fugax. Generally, these episodes are brief, lasting no longer than five minutes, and have been associated with exercise. These vasospastic episodes are not restricted to young and healthy individuals. "Observations suggest that a systemic hemodynamic challenge provoke[s] the release of vasospastic substance in the retinal vasculature of one eye."

- Giant cell arteritis: Giant cell arteritis can result in granulomatous inflammation within the central retinal artery and posterior ciliary arteries of eye, resulting in partial or complete occlusion, leading to decreased blood flow manifesting as amaurosis fugax. Commonly, amaurosis fugax caused by giant cell arteritis may be associated with jaw claudication and headache. However, it is also not uncommon for these patients to have no other symptoms. One comprehensive review found a two to nineteen percent incidence of amaurosis fugax among these patients.

- Systemic lupus erythematosus

- Periarteritis nodosa

- Eosinophilic vasculitis

- Hyperviscosity syndrome

- Polycythemia

- Hypercoagulability

- Protein C deficiency

- Antiphospholipid antibodies

- Anticardiolipin antibodies

- Lupus anticoagulant

- Thrombocytosis

- Subclavian steal syndrome

- Malignant hypertension can cause ischemia of the optic nerve head leading to transient monocular visual loss.

- Drug abuse-related intravascular emboli

- Iatrogenic: Amaurosis fugax can present as a complication following carotid endarterectomy, carotid angiography, cardiac catheterization, and cardiac bypass.

Severe ipsilateral or bilateral carotid artery stenosis or occlusion is the most common cause of ocular ischemic syndrome. The syndrome has been associated with occlusion of the common carotid artery, internal carotid artery, and less frequently the external carotid artery. Other causes include:

- Takayasu's arteritis

- Giant cell arteritis

- Severe ophthalmic artery occlusion, due to thromboembolism.

- Surgical interruption of anterior ciliary blood vessels supplying the eye, particularly during extensive strabismus surgery on 3 or more rectus muscles, leading to an anterior segment ischemic syndrome.

The cause of PMR is not well understood. The pain and stiffness result from the activity of inflammatory cells and proteins that are normally a part of the body's disease-fighting immune system, and the inflammatory activity seems to be concentrated in tissues surrounding the affected joints. During this disorder, the white blood cells in the body attack the lining of the joints, causing inflammation. Inherited factors also play a role in the probability that an individual will develop PMR. Several theories have included viral stimulation of the immune system in genetically susceptible individuals.

Infectious disease may be a contributing factor. This would be expected with sudden onset of symptoms, for example. In addition, new cases often appear in cycles in the general population, implying a viral connection. Studies are inconclusive, but several somewhat common viruses were identified as possible triggers for PMR. The viruses thought to be involved include the adenovirus, which causes respiratory infections; the human parvovirus B19, an infection that affects children; and the human parainfluenza virus. Some sufferers attribute the onset of PMR to stress.

Persons having the HLA-DR4 type of human leucocyte antigen appear to have a higher risk of PMR.

Although the exact cause is unknown, some risk factors associated with individuals with IAA are:

Tobacco Use: Cigarette smoking and other forms of tobacco use appear to increase your risk of aortic aneurysms. In addition to the damaging effects that smoking causes directly to the arteries, smoking contributes to the buildup of fatty plaques in your arteries (atherosclerosis) and high blood pressure. Smoking can also cause your aneurysm to grow faster by further damaging your aorta.

Hardening of the arteries (atherosclerosis). Atherosclerosis occurs when fat and other substances build up on the lining of a blood vessel, increasing your risk of an aneurysm.

Infection in the aorta (vasculitis). In rare cases, abdominal aortic aneurysm may be caused by an infection or inflammation that weakens a section of the aortic wall.

Carotidynia is a syndrome characterized by unilateral (one-sided) tenderness of the carotid artery, near the bifurcation. It was first described in 1927 by Temple Fay. The most common cause of carotidynia may be migraine, and then it is usually self-correcting. Common migraine treatments may help alleviate the carotidynia symptoms. Recent histological evidence has implicated an inflammatory component of carotidynia, but studies are limited. Carotid arteritis is a much less common cause of carotidynia, but has much more serious consequences. It is a form of giant cell arteritis, which is a condition that usually affects arteries in the head. Due to this serious condition possibly causing carotidynia, and the possibility that neck pain is related to some other non-carotidynia and serious condition, the case should be investigated by a medical doctor. Because carotidynia can be caused by numerous causes, Biousse and Bousser in 1994 recommended the term not be used in the medical literature. However, recent MRI and ultrasound studies have supported the existence of a differential diagnosis of carotidynia consistent with Fay's characterization.

Amaurosis fugax (Latin "" meaning "fleeting", Greek "" meaning "darkening", "dark", or "obscure") is a painless temporary loss of vision in one or both eyes.

If carotid occlusive disease results in ophthalmic artery occlusion, general ocular ischemia may result in retinal neovascularization, rubeosis iridis, cells and flare, iris necrosis, and cataract. The condition leads to neovascularization in various eye tissues due to the ischemia. The eye pressure may become high due to associated neovascular glaucoma. An ischemic optic neuropathy may eventually occur.

Carotid stenosis is a narrowing or constriction of the inner surface (lumen) of the carotid artery, usually caused by atherosclerosis.