Causes and pathogenesis
Classical polyarteritis nodosa is an independent nosological entity, though similar manifestations can be observed in secondary conditions such as rheumatoid arthritis, Sjögren's syndrome, or hairy cell leukemia.
The main triggers and risk factors are:
- Viral agents: hepatitis B and C viruses are of primary importance, less frequently cytomegalovirus, HIV, and parvovirus B19.
- Infections and toxins: streptococcal flora, medication intake (antibiotics, sulfonamides), poisons, and vaccination.
- Triggers: solar radiation promotes the manifestation of the process.
The pathogenesis is based on an immune response involving antineutrophil cytoplasmic antibodies. Polyarteritis nodosa is characterized by cytoplasmic c-ANCA interacting with proteinase-3.
Morphological changes and stages
The pathological process affects small- and medium-sized muscular arteries, predominantly at their bifurcation and branching zones due to immune complex deposition. A characteristic morphological feature is segmental fibrinoid necrosis.
In its development, the disease goes through several sequential stages:
- Acute stage: vessel walls are infiltrated by neutrophils, eosinophils, and macrophages. Characteristic beaded nodular thickenings form, and ruptures and small aneurysms up to 1 cm in size appear in necrosis zones. The vessel lumen is usually occluded by thrombi.
- Chronic stage: cellular infiltrate is replaced by mononuclear cells.
- Resolution (sclerosis): vessel lumens are completely occluded, and their walls undergo sleeve-like thickening.
A specific feature of the pathology is evolutionary polymorphism—the simultaneous presence of different stages of inflammation within the same vessel.
Clinical forms and complications
Modern nomenclature distinguishes two main forms:
- Classical polyarteritis nodosa: affects medium- and small-sized arteries, does not involve large arteries, veins, or venules, and does not lead to glomerulonephritis.
- Microscopic polyangiitis: characterized by involvement of arterioles, capillaries, and venules with the development of pneumonitis and glomerulonephritis, but without the formation of immune deposits (typical for it are perinuclear p-ANCA).
Severe complications of the disease determine its prognosis:
- Profuse bleeding due to the rupture of vascular aneurysms.
- Peritonitis resulting from intestinal perforation during ulcerative-necrotic changes.
- Renal failure, which is the most common cause of patient mortality.
Briefly: answers to topical questions
Which target organs are most frequently involved in the pathological process in polyarteritis nodosa?
In polyarteritis nodosa, the kidneys, heart, liver, gastrointestinal tract, skeletal muscles, peripheral nervous system, and skin are most frequently involved in the pathological process.
By frequency of localization, lesions are distributed as follows:
- Kidneys — renal arteries are affected (most frequently).
- Heart — coronary arteries are affected.
- Liver — hepatic arteries are affected.
- Gastrointestinal tract — mesenteric arteries are affected.
In this disease, the pulmonary circulation vessels and renal glomerular capillaries are never affected.
What macroscopic and microscopic changes develop in the kidneys in classical polyarteritis nodosa?
In classical polyarteritis nodosa, focal necrotizing inflammation of medium- and small-sized arteries develops in the kidneys, leading to infarctions.
- Microscopic changes — segmental fibrinoid necrosis of the vessel wall, thrombosis, and the formation of microaneurysms are observed. Meanwhile, renal glomerular capillaries are never affected, and glomerulonephritis does not develop.
- Macroscopic changes — not described in detail in sources, but infarctions of renal tissue are the consequence of thrombosis.
Kidney involvement often leads to arterial hypertension and is the most common cause of patient death.
Polyarteritis nodosa = P (polyarteritis/nodules-aneurysms at bifurcations), P (polymorphism of stages in a single vessel), H (hepatitis B and C as the main cause).
Class and exam questions
Which vessels are affected in classical polyarteritis nodosa?
Medium- and small-sized muscular arteries are affected. Large arteries, as well as veins, venules, and arterioles, are not involved in the process in the classical form.
What is evolutionary polymorphism?
This is a specific feature of morphogenesis where different stages of changes are simultaneously detected in the same vessel: from acute inflammation with necrosis to resolution into sclerosis.
What antibodies are characteristic of polyarteritis nodosa?
It is characterized by cytoplasmic antineutrophil cytoplasmic antibodies (c-ANCA) reacting with proteinase-3.
What is the main cause of death in this disease?
The most common cause of patient death is developing renal failure.
What else to study on this topic
- Microscopic polyangiitis: morphological and mechanistic differences
- The role of hepatitis B virus in the induction of systemic vasculitides
- Differential diagnostics of c-ANCA and p-ANCA associated vasculitides
- Pathomorphology of secondary vasculitides in rheumatic diseases
- Dynamics of vascular remodeling during the resolution of vasculitis into sclerosis
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