This topic can be discussed without any limit for any number of days,weeks or for years. This is a that much vast area. But today I am going to tell you something about vasculitis from a point of view of an undergraduate medical student, who need a way to keep things in an orderly fashion, before they more on to very sophisticated, complex details beyond the level of an undergraduate.
Vasculitis is a general term for inflammation in the vessel wall. Signs and symptoms of these conditions greatly vary depending on the vasculature of which system they affect or affect most. If something to be kept in mind, we need to develop an order. To develop an order, we need to categorize properly.
There are various categories being introduced. But as Undergraduates, there are certain important vasculitis conditions we must know and I have used my own way of classifying as follows. You can make your own classid=fication and find your own way to make things easy for you, if you are willing to read.
Namely Giant cell arteritis, Takayasu arteritis, Polyarteritis nodosa, Kawasaki disease, Microscopic polyangitis, Wegener’s disease, Churg – strauss syndrome, Systemic Lupus Erythromatosis (SLE), Immunoglobulin A mediated vasculitis/nephropathy and vasculitis conditions caused by infections are very important and carries a great importance. So I am going to talk about them according to the ABOVE SHOWN CLASSIFICATION, elaborating following areas in each vasculitis condition;
- Size of vessels affected ( LARGE/MEDIUM/SMALL)
- Population demographics (most occurring age, male/female preponderance)
- Mostly affected systems
- Morphology ( granulomatous?, Necrotizing?, thrombosis?, embolization? , etc)
- Clinical features
There are two main vasculitis conditions occurring in LARGE TO MEDIUM SIZED MUSCULAR ARTERIES. They are GIANT CELL ARTERITIS and TAKAYASU ARTERITIS. The main demo-graphical difference between these two is, giant cell arteristis mostly occur in people above 50 years of age and Takayasu occurs in people who are younger than 50 years.
Giant cell arterits mostly occurs in Aorta and its called Giant cell Aortitis. It is also occuring in temporal arteries leading to Temporal arteritis. This begets a severe, sudden, intermittent, unilateral, throbbing type Headache which mimics a migraine attack. When diagnosing a migraine patient taking this into consideration would be critical in managing the patient. Granulomas are found, but it is NOT a narcotizing lesion. The key morphological feature is “Medial granulomatous inflammation”. There is fragmentation of internal elastic lamina, where inflammation is centred with the ivasion of mono nuclear cell aggregates.
Takayasu arteritis mainly occurs in Arch of Aorta, often with great vessels . It is also characterized by granuloma formations. In contrast to above, here we can see patchy necrosis of media (it is considered rare). Key morphologica feature is intimal hyperplasia along with perivascular cuffing of mononuclear cells around vasa vasorum, which supplies blood to media. This would compromise the oxygen and nutrient supplies to media and media will be subjected to destruction. This is repleted by GIANT CELLS, and patchy medial necrosis occurs. Even though this mostly involves the ARCH OF AORTA and the Great vessels, this can involve or progress in to any part of the aorta. Depending on the parts involved, clinical picture is determined. When Arch and the great vessels are involved, as the lumen narrows, the blood supply to upper extremities are limited. This will lead to diminished pulses in upper limbs. This is typically called,”Pulse less Disease”. if it involves the lower part of aorta, it can lead to claudication. If pulmonary vasculature is involved, it would lead to pulmonary hypertension and if renal vasculature is involved, it would lead to hypertension.
Vasculitis conditions occurring mainly in small to medium sized arteries are caused by 2 main mechanisms. One is Immune-complex mediated and the other is Anti endothelial cell antibodies mediated. There is a major difference between these two conditions with respect to the age where we can observe these conditions most. Polyarteritis nodosa occurs typically in young adults, who are less than 40 years with a male preponderance of 2:1 (Male:Female). Kawasaki disease occurs mainly in children who are 4 years or younger than that.
Polyarteritis nodosa is a vaculitis condition where there is NO granuloma formation, but there is a Necrosis ( this is called fibrinoid necrosis, a special type of a necrosis occurig in blood vessels). This necrosis occurs mainly at the branching points of a vessels and it will be circumferential. Once the necrosis occurred, the lumen will be narrowed and as the endothelium is damaged, it would be prone to formation of a thrombus. Both these will cause reduced blood supply to the level below the narrowing causing ulceration, ischemia, infarction and hemorrhages. Depending on the system affected the clinical picture would vary. The MOSTLY AFFECTED SYSTEM IS RENAL system. Renal arteries mainly at the branching point from the aorta, are narrowed and the tissue perfusion is reduced. As a result rapidly progressing hypertension and hematuria can occur. Next in line is the heart and then the Gastro-intestinal system. If the vasculature of the Gastro-intestinal system is involved, we can expect the patient to have bloody stools and abdominal pain.
Kawasaki disease is the leading cause of Myocardial infractions in childhood which is mediated by Anti Endothelial Cell Antibodies. The morphological features are more or less the similar to what happens in Polyarteritis Nodosa. Due to luminal narrowing because of Fibrinoid necrosis, and thrombus formation again because of the fibrinoid necrosis, it leads to ischemia and ultimately to infarction.
When moving on to vasculitis conditions occurring in small arteries to arterioles and capileries, again there are two main ways where we can make a distinct. Almost every condition mentioned under this topic are caused by immune complexes or else immune mediated. but in one category, these immune cells are sparse in the circulation. Therefore they are called ,”Pauci-immune” conditions, and in the other category immune coplexes are abundantly found in circulation.
Pauci-immune group consits of 3 main diseases where the pathologand morphoogy is more or less similar to Polyarteritis Nodosa with few exceptions. In all of these conditions a factor called, Anti Neutrophil Cytoplasmic Antibodies (ANCA) are present. There are two types of ANCA as p-ANCA and c-ANCA. C-ANCA is predominantly found in Wegener’s granulomatosis (Microscopic polyangitis with gralnulomatosis) and p-ANCA is predominantly present in Microscopic polyangitis.
Microscopic polyangitis is carrying similar morphology and pathology to Polyarteritis nodosa, except that they affect mainly capillaries and the fibrinoid necrosis occuring is NOT CIRCUMFERENTIAL; it is rather a SEGMENTAL TYPE NECROSIS. Here glomeruli are directly feted, and if something is destroying glomeruli of a nephrone, it’s ability to regenerate is completely compromised. Microscopic Polyangitis can be a feature of many diseases such as Henoch-Schonlein purpura, essential mixed cryoglobulinemia, etc. Depending on the system/organ invloved again as in polyarteritis nodosa you can work out the clinical features such as haemoptysis, heaturia, bloody stools, proteinuria, abdominal pain etc.
Granulomatosis with polyangitis (eralier Known as “Wegener’s Granulomatosis), name it self implies that it is a condition where polyangitis occurs with granulomatosis. Morphology and the pathology will be very much similar to Microscopic polyangitis, but this time with a granulomatosis. Still they are affecting capillery systems (same as Microscopic polyangitis), but this time they are more concentrated on the repiratory system; Lungs and upper airways mostly. So there will Necrotizing granuolomas in upper airways with persistant pneumonitis, chronic sinusitis with mucosal ulceration of nasopharynx, etc . It also affects renal vasculature. It has a classical morphological feature with regard to renal aspect called,”Focal, Necrotizing, Crescentinc glomerularnephritis”.
Churg-strauss syndrome also carries similar morphology to both above conditions, it differs from microscopic polyangitis as it shows granulomatosis with eosinophilia, and from Wegener’s disease as this time they have eosinophilia. This condition also concentrates more on respiratory tract. In addition to above mentioned clinical features under Wegener’s, we have to add ASTHMA to churg-strauss as eosinophilia in respiratory tract can lead to asthma. One of the application where Leukotriene receptor antagonists can be used as drugs is this condition, as in this condition it is being reported that leukotriene receptors have been triggered in churg strauss syndrome.
I hope I could be some assistance to figure out that its not that difficult to keep vasculitis in mind. I know there are so many other things to be included under these. But every leap begins with a single step. Try to find your own way. Then first make a STRUCTURE/MOCK-UP/A SKETCH. Then start adding details in a systematic way. It would make your work efficient and easy to recall anything you want ASAP…!!