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Schönlein-Henoch disease: causes and pathogenesis
Last reviewed: 23.04.2024
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The causes of purple Shonlein-Tenoch are associated with infections, food allergies, drug intolerance, and alcohol consumption. In most cases, the disease is preceded by nasopharyngeal or intestinal infection. The development of hemorrhagic vasculitis is associated with a number of bacteria and viruses. The relationship of the disease with infection caused by streptococci and staphylococcus, cytomegalovirus, parvovirus B19, human immunodeficiency virus was most clearly traced. Less often note the association with bacteria of the intestinal group, iersinia, mycoplasmas.
The development of purple Shonlein-Genoch after the use of certain drugs, including vaccines and serums, antibiotics (penicillin), thiazide diuretics, quinidine, is described.
The pathogenesis of the purple Schoenlein-Henoch is not fully understood. Currently, an important pathogenic role is played by IgA, its macromolecular polymers and IgA-containing immune complexes. It has been established that 40-50% of patients increased IgA concentration in the blood, mainly by increasing the polymeric forms of IgA isotype r In some cases these IgA, exhibit properties rheumatoid factor, antibody to the cytoplasm of neutrophils, form complexes with fibronectin. The reason for the increase in IgA is both an increase in its synthesis and a decrease in clearance, possibly as a result of a defective biochemical structure of IgA, which contributes to the lengthening of the period of circulation of IgA polymers and IgA-containing immune complexes in the systemic circulation.
The development of glomerulonephritis in hemorrhagic vasculitis is associated with the deposition of IgA-containing immune complexes in the mesangium, followed by the activation of complement in an alternative pathway. The possibility of forming immune complexes in situ is also discussed . The latter mechanism is supported by the presence of mesangial deposits of IgA in patients with normal blood levels, the absence of IgA-containing immune complexes in the glomeruli of the majority of HIV-infected individuals who have a high level of polymeric IgA in the blood plasma. On the basis of these facts, it was suggested that there is a mechanism that facilitates the deposition of IgA in the glomeruli. As such a mechanism, the currently established defect of the glycosylation of IgA molecules with Schonlein-Henoch purpura is considered. As a result, a change in the structure of IgA is possible, which in turn disrupts its interaction with mesangial matrix proteins, receptors on the mesangial cell surface, complement (altered IgA resulting from abnormal glycosylation, more efficiently activates complement than normal), causing the deposition of immune complexes with subsequent damage to the glomerulus.
Changes in the concentration of IgA in the blood, the presence of its polymeric forms and IgA-containing deposits in the glomeruli of the kidney and the clinical and morphological features of glomerulonephritis in Schonlein-Henoch purpura do not differ from those in IgA-nephropathy. In connection with this, discussions are still ongoing on whether it is possible to consider Berger's disease as a local renal form of purpura Schonlein-Henoch. Recently, the possible role in the pathogenesis of purpura Schonlein-Henoch chronic inflammation of the intestinal wall, due, apparently, to the violation of the function of its local immune system. This assumption is based on the increase in intestinal permeability for macromolecules established in recent studies in the exacerbation of the disease and the discovery of the relationship between the permeability of the intestinal mucosa and the severity of infiltration by the last lymphocytes.
[Pathology of Shenlen-Henoch disease
Morphological changes in the kidneys with Schönlein-Henoch purpura are various.
Most often, a picture of focal or diffuse mesangioproliferative glomerulonephritis is noted.
Less common is diffuse proliferative endocapillary glomerulonephritis, which is characterized by a combination of intense mesangial proliferation with an increase in mesangial matrix, the presence of leukocytes in the lumen of glomerular capillaries and foci of doubling the basal membrane of the glomeruli.
In a small part of the patients, diffuse proliferative glomerulonephritis with endocapillary and extracapillary proliferation is revealed, in which, depending on the severity of the lesion, along with diffuse proliferative changes, half-moon formation in less than or more than 50% of the glomeruli and mesangiocapillary glomerulonephritis are noted.
Tubulo-interstitial changes in the early stages of the disease are expressed minimally, at later times are represented by canal atrophy and interstitium sclerosis, which correlates with the severity of glomerular pathology. In adults, unlike children, arteriosclerosis and arteriolar hyalinosis are often found.
Immunofluorescence microscopy in patients with Shonlein-Genoch purpura reveals diffuse granular deposits, mainly containing IgA, in mesangium. These deposits can then penetrate the capillary wall, located subendothelial. Subepithelial localization of deposits is extremely rare. In some cases, deposits of IgG in combination with IgA are detected. Virtually all patients with IgA-nephritis with Schönlein-Henoch purpura have C3 deposits, in more than 80% of cases - fibrinogen deposits in mesangium, which indicates local intravascular coagulation in the glomeruli of the kidney.