Etiology and triggering factors
Hemorrhagic vasculitis is a classic example of an immunopathological process. Epidemiological data clearly indicate that in the vast majority of cases, the disease affects pediatric patients, predominantly in the younger age group.
A thorough history taking usually reveals that the development of the full clinical picture is preceded by a recent upper respiratory tract infection. The etiology of the disease is multifactorial, but it is always based on an inappropriate, allergic effect of various microorganisms on the patient's immune system. Among the most significant infectious agents capable of acting as triggers are:
- Bacterial pathogens: primarily streptococci, as well as mycoplasmas, yersinia, and legionella.
- Viral agents of various groups.
However, infections are not the only triggering factor. The pathological process can be triggered by the intake of certain medications, against the background of severe food allergies, after insect bites, or even as a result of a simple yet severe hypothermia of the body.
Pathogenesis and morphological picture
From the perspective of pathomorphology, the central link in the pathogenesis is the formation of circulating immune complexes. The characteristic feature of this vasculitis is that these complexes invariably contain IgA class immunoglobulins and complement system components. These macromolecular structures circulate in the bloodstream and ultimately deposit on the endothelial lining of blood vessels.
The target for the deposition of immune complexes is the microvasculature, predominantly capillaries. The fixation of complexes on the endothelium instantly triggers a cascade of local inflammatory reactions, leading to characteristic morphological changes that a pathologist observes under a microscope:
- Fibrinoid necrosis. The walls of the affected vessels of the microvasculature undergo profound destruction. There is destruction of cellular elements and the basement membrane; the wall becomes impregnated with fibrin and loses its normal structure.
- Perivascular leukocytic infiltration. In response to necrosis and complement activation, inflammatory cells rush to the lesion site. Dense clusters of leukocytes form around the destroyed capillaries.
- Diapedetic hemorrhages. Due to fibrinoid necrosis, the capillary wall loses its barrier function. Erythrocytes freely leave the vascular bed via diapedesis, infiltrating the surrounding tissues and forming microscopic, and subsequently macroscopic, foci of hemorrhage.
Clinical manifestations and renal involvement
The clinical picture of hemorrhagic vasculitis is a direct reflection of the morphological changes described above. Since capillaries are present in all tissues, the disease is systemic in nature, but has favored localizations: the skin, joints, gastrointestinal tract, and kidneys.
Classic manifestations include:
- Skin changes. Fine punctate purpuric rash is observed. Due to the combination of inflammatory edema of the vessel wall and diapedetic hemorrhages, the rash elements slightly rise above the skin surface, forming the so-called palpable purpura.
- Joint syndrome. Patients complain of pronounced polyarthralgia (pain in multiple joints simultaneously), which is associated with involvement of the capillary-rich synovial membrane.
- Systemic reactions. Fever predictably develops as a response to systemic immune inflammation.
The most formidable manifestation determining the severity of the course and the prognosis for the patient's life is renal syndrome. The deposition of IgA-containing complexes in the capillaries of the renal glomeruli leads to the appearance of blood (hematuria) and protein (proteinuria) in the urine. Morphological examination of renal biopsy samples reveals a pattern of focal segmental proliferative glomerulonephritis. In an unfavorable, progressive course, the process can transform into extracapillary glomerulonephritis. This is a severe lesion of the renal filtration apparatus capable of leading to the development of renal failure.
Briefly: answers to topical questions
What macroscopic and microscopic changes develop in the wall of the gastrointestinal tract in hemorrhagic vasculitis?
In hemorrhagic vasculitis, macroscopic examination of the gastrointestinal tract wall reveals thickening of the intestinal wall caused by intramural hemorrhage; gastrointestinal bleeding is possible. Microscopic examination reveals changes in the microvasculature vessels:
- fibrinoid necrosis of the vessel walls;
- diapedetic hemorrhages;
- perivascular leukocytic infiltration.
What abdominal surgical complications can occur in the abdominal form of hemorrhagic vasculitis?
The abdominal form of hemorrhagic vasculitis can cause:
- gastrointestinal bleeding;
- ileo-ileal intussusception, which occurs most frequently, often reduces spontaneously, and does not require pneumatic or hydrostatic reduction;
- ileocolic intussusception, which may occur and must be treated according to idiopathic intussusception protocols.
With which hemorrhagic diatheses is Schönlein-Henoch purpura to be differentiated?
Schönlein-Henoch purpura must be differentiated from hemorrhagic diatheses characterized by other types of bleeding:
| Disease | Type of bleeding | Affected component |
|---|---|---|
| Thrombocytopenic purpura | Petechial-ecchymotic | Platelet link |
| Hemophilia | Hematomal | Coagulopathy |
| Von Willebrand disease | Mixed, petechial-hematomal | Hemostasis disorder |
| Hemorrhagic angiomatosis | Angiopathy | Vascular wall |
Hemorrhagic diatheses also include vitamin C deficiency and hemorrhagic metropathies.
For quick memorization of the main target organs in capillarotoxicosis, use the acronym S-J-K-R: Skin (purpuric rash), Joints (polyarthralgia), Kidneys (hematuria, proteinuria, nephritis), R (GI tract) [Note: Russian mnemonic translated conceptually].
Class and exam questions
Which immunoglobulins play the main role in the pathogenesis of hemorrhagic vasculitis?
Circulating immune complexes containing IgA class immunoglobulins and complement fractions play the leading role. They deposit on the vascular endothelium and trigger inflammation.
What type of necrosis is characteristic of the affected vessels in this disease?
Fibrinoid necrosis of the microvasculature vessel walls, accompanied by destruction of the endothelium and fibrin imbibition of the wall, is specific to hemorrhagic vasculitis.
What is the mechanism of hemorrhagic rash formation?
The rash is formed due to diapedetic hemorrhages. Due to necrosis and inflammation, the capillary wall loses its barrier function, and erythrocytes escape into the surrounding tissues.
What are the risks of kidney involvement in Schönlein—Henoch purpura?
The deposition of complexes in the glomeruli causes proliferative or extracapillary glomerulonephritis. This condition can progress and lead to severe renal failure.
What else to study on this topic
- The mechanism of formation of IgA-containing immune complexes in respiratory tract infections.
- Morphological differences between focal segmental and extracapillary glomerulonephritis.
- Pathogenesis of diapedetic hemorrhages in microvascular lesions.
- Differential diagnosis of palpable purpura in various systemic vasculitides.
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