Classicpolyarteritis nodosa (PAN or c-PAN) is a systemic vasculitis characterized by necrotizing inflammatory lesions that affect medium-sized and small muscular arteries, preferentially at vessel bifurcations, resulting in microaneurysm formation, aneurysmal rupture with hemorrhage, thrombosis, and, consequently, organ ischemia or infarction.
Kussmaul and Maier first described PAN in 1866. The autopsy of a patient with fever, weight loss, abdominal pain, and polyneuropathy revealed areas of focal inflammatory exudations that gave rise to palpable nodules along the course of medium-sized arteries.[1] PAN, like other vasculitides, affects multiple systems and has protean manifestations, although it most commonly affects skin, joints, peripheral nerves, the gut, and the kidney.[2] The lungs are usually spared with PAN. A typical PAN patient might present with fever, night sweats, weight loss, skin ulcerations or tender nodules, and severe muscle and joint pains developing over weeks or months. (See Etiology, Clinical, and Workup.)
Nonspecific, firm, tender subcutaneous nodules without livedo reticularis and/or systemic involvement may be the first sign of polyarteritis nodosa (PAN). Insight into PAN requires some understanding of how this rare disease has been defined. Periarteritis nodosa was a term used from the mid 1800s to the 1900s to describe a spectrum of systemic vasculitic disorders, including diseases that manifested as arterial aneurysms, as well as those that caused diffuse necrotizing glomerulonephritis.[3, 4] The term periarteritis nodosa was changed to polyarteritis nodosa in the mid 1900s to reflect the transmural inflammation of arteries caused by this disorder.[5]
The understanding of vasculitides continued to increase by the 1980s with the discovery of antineutrophil cytoplasmic antibodies (ANCAs). Microscopic polyangiitis
(MPA; formerly called microscopic polyarteritis) is an ANCA-associated systemic vasculitis that has some features similar to those of classic PAN, with the additional involvement of renal glomeruli and pulmonary capillaries.
In the chronic stage, fibrinoid necrosis of the vessels causes thrombosis and tissue infarction. Aneurysmal dilatations of the involved arteries, as large as 1 cm in size, are characteristic findings of PAN. Kidney lesions show predominant arteritis without glomerulonephritis; however, in patients with severe hypertension, glomerulosclerosis may be superimposed with glomerulonephritis. Pulmonary arteries are not involved, and bronchial artery involvement is uncommon.
Kussmaul and Maier first described PAN in 1866. The autopsy of a patient with fever, weight loss, abdominal pain, and polyneuropathy revealed areas of focal inflammatory exudations that gave rise to palpable nodules along the course of medium-sized arteries.[1] PAN, like other vasculitides, affects multiple systems and has protean manifestations, although it most commonly affects skin, joints, peripheral nerves, the gut, and the kidney.[2] The lungs are usually spared with PAN. A typical PAN patient might present with fever, night sweats, weight loss, skin ulcerations or tender nodules, and severe muscle and joint pains developing over weeks or months. (See Etiology, Clinical, and Workup.)
Nonspecific, firm, tender subcutaneous nodules without livedo reticularis and/or systemic involvement may be the first sign of polyarteritis nodosa (PAN). Insight into PAN requires some understanding of how this rare disease has been defined. Periarteritis nodosa was a term used from the mid 1800s to the 1900s to describe a spectrum of systemic vasculitic disorders, including diseases that manifested as arterial aneurysms, as well as those that caused diffuse necrotizing glomerulonephritis.[3, 4] The term periarteritis nodosa was changed to polyarteritis nodosa in the mid 1900s to reflect the transmural inflammation of arteries caused by this disorder.[5] The understanding of vasculitides continued to increase by the 1980s with the discovery of antineutrophil cytoplasmic antibodies (ANCAs). Microscopic polyangiitis
(MPA; formerly called microscopic polyarteritis) is an ANCA-associated systemic vasculitis that has some features similar to those of classic PAN, with the additional involvement of renal glomeruli and pulmonary capillaries.
Features of PAN
The American College of Rheumatology (ACR) established criteria for research purposes in order to differentiate PAN from other forms of vasculitis.[6] A committee of ACR physicians selected 10 disease features of PAN; in order for PAN to be diagnosed, at least 3 of the 10 ACR criteria should be present when radiographic or pathological diagnosis of vasculitis is made[6] (See Clinical and Workup.):- Weight loss of 4 kg or more
- Livedo reticularis
- Testicular pain/tenderness
- Myalgia or leg weakness/tenderness
- Mononeuropathy or polyneuropathy
- Diastolic blood pressure greater than 90 mm/Hg
- Elevated blood urea nitrogen (BUN) or creatinine level unrelated to dehydration or obstruction
- Presence of hepatitis B surface antigen or antibody in serum
- Arteriogram demonstrating aneurysms or occlusions of the visceral arteries
- Biopsy of small- or medium-sized artery containing polymorphonuclear neutrophils
Stages
PAN is divided into subacute, acute, and chronic stages. In the subacute stage, infiltration of mononuclear cells becomes more prominent, while in the acute stage, polymorphonuclear neutrophils infiltrate all layers of the vessel wall. (See Etiology.)In the chronic stage, fibrinoid necrosis of the vessels causes thrombosis and tissue infarction. Aneurysmal dilatations of the involved arteries, as large as 1 cm in size, are characteristic findings of PAN. Kidney lesions show predominant arteritis without glomerulonephritis; however, in patients with severe hypertension, glomerulosclerosis may be superimposed with glomerulonephritis. Pulmonary arteries are not involved, and bronchial artery involvement is uncommon.
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