Vascular Pathology - Vasculitis

The word Vascular refers to the blood vessel, and there are three types of blood vessels which are the Capillaries, Arteries, and Veins. You must have been thought this in your elementary biology. The arteries are muscular for the purpose of withstanding blood pressure, and they are also elastic so they can be able to maintain the blood pressure. Veins are the next vessels which are less muscular with high compliance and the capillaries are single layered, thin vessels which are close to the muscles to be distributed blood and they are responsible for the diffusion of nutrients to and away from the tissues. The vessels are made up of the Tunica intima, Tunica media, and Tunica adventitia but there are difference in the thicknesses of the wall. The tunica intima is the inner layer of the vessel made up of the endothelium, basal lamina, and sub-endothelial layer. There is an internal elastic lamina between the innermost tunica intima and the Tunica media. The tunica media is made up of smooth muscle layers which is responsible for the elasticity causing contraction and relaxation of the vessels. Also, there is the external elastic lamina between the Tunica media and the Tunica adventitia. The Tunica adventitia is elastic and collagenous, made up of Vasa vasorum, and Nervi Vascularis. After giving a little explanation of the vessels, let's discuss a vascular pathology, and in this post, we will look at Vasculitis.

Vasculitis, which is literally known as Vessel Inflammation. Vasculitis causes inflammation of the blood vessels and tissue damage, causing fever, malaise, Weakness, Myalgia, and joint pain. Vasculitis can cause some symptoms as a result of its downward ischemia which includes thrombosis, and vessel injury. Vasculitis can be classified based on the vessel sizes which are classified as small vessel vasculitis, medium vessel vasculitis, and large vessel vasculitis. It can also be classified based on vessel sites and the basis of lesion histology, such as neutrophilic, lymphocytic, eosinophilic, and granulomatous. It can also be classified based on clinical manifestations, pathogenesis, and Etiology which can be classified as infectious and non-infectious vasculitis. The infectious causes can be bacterial, fungi, or viral, and is less common. The non-infectious causes can be immune mediated, as a result of injury, caused by chemicals, and trauma. This is more common than the infectious causes of vasculitis.

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Both Infectious and injurious causes of vasculitis can lead to endothelial injury leading to fibrosis, and thrombosis. When the vasculitis is immune mediated, it can be immune complex mediated vasculitis (antigen-antibody mediated complex) where the immune complexes are deposited in the endothelial cell leading to edothelial damage by cytokine release, Anti Neutrophilic Cytokines Antibodies (ANCAs) Mediated Vasculitis which are auto antibodies going against the granules in the neutrophils. Last is the Anti Endothelial Cell Mediated Antibodies Vasculities which is as a result of antibodies working against antigens in the endothelial cell causing Cytotoxicity.

Small vessel vasculitis include Wegener's Granulomatosis which specifically affects the upper airways causing sinusitis, rhinitis, and saddle nose, the lower respiratory tract, the kidneys causing hematoria, Red Blood Cell coste, necrotizing glumerulonephritis, and the lungs causing nodules. Another small vessel vasculitis is Microscopic polyangiitis, and it does not have granulomas. It is the necrotizing vasculitis of numerous organs in the body especially the kidney and the lungs. This will lead to palpable purpura, pulmonary capillary hemoptysis, alveolitis, fibrinoid necrosis, leukocytoclastic vasculitis, and necrotizing glomeruloneph. Churg Strauss Syndrome is another type of vasculitis, and it is also known as allergic granulomatosis. It is a necrotizing inflammation with Eosinophillia that involves the lungs and the heart. The patients would have heart problems, rashes, asthma, lungs infitrates, sinus problems, and nasal blockage. Another vasculitis is Henoch Schonlein Purpura which is an IgA immune complexmediated vasculitis. IgA is present in mucusal surface and it is common in children with upper respiratory tract infection.

In the medium vessel vasculitis, I will be starting with Polyarteritis Nodosa which is a necrotizing vasculitis of the heart, kidney, gastrointestinal tract, and the Liver but not the lungs. It is an immune complex in the intima basically by hepatitis B antigen. It can cause segmental necrotic vasculitis and these lesions can be divided into acute and healed lesions. Another Vasculitis is Kawasaki's disease also known as Mucocutaneous lymph node syndrome, which has clinical manifestation that displays with conjuctival and oral erythema, skin rash, and lymphodenopathy. It involves the coronary artery and it is common in children less than 4 years with an etiology of the T-cell hypersensitivity to unknown antigens.

When it comes to Vasculitis, the Giant Cell (Temporal) Arteries is the high yield of all vasculitis which involves the thickening and fragmentation of lamina, having high ESR, jaw claudication and patient having temporal headache, polymyalgia Rheumatica, and Visual Problems.

• https://www.ncbi.nlm.nih.gov/books/NBK545186/
• https://www.nhlbi.nih.gov/health/vasculitis/causes
• https://arthritis-research.biomedcentral.com/articles/10.1186/ar2193
• https://emedicine.medscape.com/article/1008239-overview
• https://www.jacionline.org/article/S0091-6749
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2855433/
• https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.120.046657
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908435/