| • | affects small and medium sized muscular arteries of such caliber as coronary vessels and subcutaneous tissue |
| • | focal vasculitis forms nodose swellings that become necrotic, producing aneurysms and rupture of the vessel |
| • | characteristically the arteries are affected at their bifurcations |
| • | histology is mainstay of diagnosis, otherwise angiography may detect aneurysmal dilations |
| • | histology: in skin, a necrotizing vasculitis in the muscular arteries at the dermal-subcutaneous interface |
benign cutaneous Pan
| • | remarkable for an absence of visceral involvement |
| • | patients often have recurrent skin, joint, and muscle involvement without involvement of the vital organs |
| • | cutaneous findings similar to those of the systemic form |
| • | both have predilection for lower extremities |
| • | both may have crops of red, tender, subcutaneous nodules surrounded by livedo reticularis |
| • | = “starburst appearance” |
| • | the secondary panniculitis may assume a lobular pattern (ddx = early nodular vasculitis) |
| • | histology: identical to PAN except only the small and medium arteries at the dermal-subcutaneous border are involved |
systemic PAN
| • | skin is involved in 40% of patients with systemic PAN with wide ranging findings |
| • | most striking and diagnostic lesions are subcutaneous nodules distributed along the course of the superficial arteries |
| • | these nodules are painful and may in time ulcerate |
| • | may be associated with livedo reticularis pattern involving the adjacent cutaneous surface |
| • | may involve vessels throughout entire body, though typically lungs not involved |
| • | (70%) renal complications - glomerulosclerosis |
| • | (60%) peripheral neuropathy - mononeuritis multiplex, most often manifest as a foot drop, is a hallmark of PAN |
| • | arthralgia, MI, GI infarction |
| • | CBC (WBC as high as 40, with 80% neuts) |
| • | Hep B and C serology; p ANCA (microscopic polyangiitis) and c ANCA |
| • | UA for proteinuria, hematuria, and casts |
hepatitis B and PAN:
| • | detect HepBsAg ~ 10 to 50% of patients with PAN |
| • | immune complex mechanism for Hep B associated PAN |
| • | a subset of systemic PAN that fulfill the following criteria: |
| • | segmental necrotizing and crescenteric glomerulonephritis |
| • | associated with extrarenal vasculitis involving small-sized vessels |
| • | without granulomas or asthma |
| • | some authors classify MP with Wegener’s of Churg-Strauss because of similar cutaneous and histologic findings as well as the association with ANCA’s in all three disorders |
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