What is the difference between IgA nephropathy and Henoch-Schönlein purpura nephritis?

Mesangial expression of angiotensin II receptor in IgA nephropathy and its regulation by polymeric IgA1

BACKGROUND

Enhanced gene expression for the renin-angiotensin system (RAS) is detected in glomerular mesangial cells in IgA nephropathy (IgAN). Preliminary studies showed a reduced glomerular gene expression of angiotensin II subtype 1 receptor (AT1R), suggesting a regulatory response to high intrarenal angiotensin II (Ang II) concentration in IgAN.

METHODS

We examined the effect of polymeric IgA1 (pIgA1) from patients with IgAN on the expression of Ang II receptors in cultured human mesangial cells (HMC).

RESULTS

Polymeric IgA1 from patients with IgAN down-regulated the expression of AT1R in HMC in a dose-dependent manner. When similar experiments were conducted with addition of an angiotensin-converting enzyme inhibitor (captopril) or an AT1R antagonist (losartan), there was a significant increase in the expression of AT1R. Blockade of Ang II with captopril or losartan alone resulted in a stepwise increase of AT1R in cultured HMC. Down-regulation of Ang II subtype 2 receptor (AT2R) was not observed in HMC cultured with pIgA1 from patients with IgAN. The acute suppressive effect of pIgA1 from IgAN on the expression of AT1R was confirmed in HMC incubated with IgA isolated from 15 IgAN patients, 15 healthy subjects, and other glomerulonephritides control subjects. Reduced glomerular expression of AT1R (but not AT2R) was also demonstrated in renal biopsies from patients with IgAN.

CONCLUSION

Our findings demonstrate an altered AT1R expression in HMC in response to raised intrarenal Ang II in IgAN. Our in vitro studies also support that an imbalance of AT1R and AT2R activity in HMC following exposure to pIgA plays a significant pathogenetic role in the inflammatory injury in IgAN.

Pathogenesis of IgA nephropathy

In IgA nephropathy (IgAN), there is dysregulation of the IgA response to a wide range of antigens. The dysregulation promotes synthesis of polymeric IgA1 (pIgA1) with physicochemical characteristics that favor mesangial deposition, including altered O-glycosylation of the hinge region. This may be the synthesis of IgA in the systemic compartment, which has the phenotype of mucosal IgA. There is not a change in IgA1 structure to an entirely abnormal form; rather, there is a shift that results in a proportional increase in forms of IgA1 also found in healthy individuals. Altered O-glycosylation could favor pIgA1 deposition by promoting formation of macromolecular IgA and immune complexes. Mesangial injury follows through interactions of pIgA1 with the cells and extracellular matrix proteins of the mesangium and the activation of complement. The final clinical expression of IgAN also depends on generic factors, including hypertension and proteinuria, and a fibrotic renal response. No single "IgAN gene" has been identified, and it is likely that multiple interacting genes will eventually prove to underlie susceptibility to IgAN and the risk of progressive renal disease. These new pathogenic insights have not yet led to new therapeutic opportunities.

Elevated levels of anti-Helicobacter pylori antibodies in Henoch-Schönlein purpura

OBJECTIVE

Henoch-Schonlein purpura (HSP) is a systemic vasculitis characterized by IgA-containing deposits in the skin, joints, gastrointestinal mucosa and glomeruli. HSP is much rarer in adults than in children. Among a number of other pathogenic factors, Helicobacter pylori (Hp) has recently been implicated in the gastrointestinal and extra-gastrointestinal manifestations underlying HSP. We aimed at studying the occurrence of Hp infections in 11 adult HSP patients with appearance in our clinical practice in the last 5 years.

METHODS

Eleven adult HSP and 20 healthy adult patients were recruited for this study. Anti-Hp IgG and IgA antibodies were assessed in sera of HSP patients with active (n = 5) and remittent disease (n = 6) and healthy controls (n = 20) in the context of clinical symptoms, endoscopic evaluation, as well as routine and immunolaboratory observations. Concurrent Hp infection was confirmed by urease test and histology.

RESULTS

Anti-Hp antibodies were present in 10/11 of HSP patients, and 11/20 of healthy controls. However, only 4/11 HSP patients had concurrent Hp infection as confirmed by urease test and/or histology. In the healthy controls the actual Hp infection was detectable in 9/20 cases. Patients in the acute phase had significantly higher levels of anti-Hp IgG compared to healthy controls (86.0 +/- 32.0 versus 25.5 +/- 28.5 U/ml, p < 0.05). In contrast, anti-Hp IgA/IgG ratios were significantly higher in the remitting phase compared to the control group (3.1 +/- 1.8 versus 0.8 +/- 0.5 ratio, p < 0.05). Among other immunolaboratory markers, serum CRP, circulating IgA and serum tumor necrosis factor-alpha levels were significantly increased in acute patients compared to healthy group results (45.3 +/- 22.7 versus 4.8 +/- 3.5 mg/l, p < 0,05); (58.9 +/- 18.2 versus 25.2 +/- 6.4pg/ml, p < 0,05); (5.5 +/- 1.1 versus 2.4 +/- 1.2 g/l; respectively, p < 0.05).

CONCLUSIONS

Hp infection may be associated with the development and progression of HSP. IgG antibodies to Hp may be present mostly in acute HSP, while IgA antibodies may be involved in sustaining gastrointestinal symptoms underlying the chronic phase of the disease.

Diagnosis of Henoch-Schönlein purpura: renal or skin biopsy?

Henoch-Schönlein purpura (HSP) is a form of systemic vasculitis characterized by vascular wall deposits of predominantly IgA, typically involving small vessels in skin, gut, and glomeruli and associated with purpura, intestinal colic, hematuria, and arthralgia or arthritis. HSP nephritis leads to chronic renal failure in up to 20% of pediatric patients after 20 years of follow-up in selected series. The risk is related to the initial clinical presentation and is maximal (more than 50%) when initial signs are a combination of nephrotic and nephritic syndromes. Although less important, the risk persists for mild renal symptoms or when the patient has apparently completely recovered from the renal disease. Other types of non-IgA-related leukocytoclastic vasculitis may be difficult to discriminate from HSP, thus confounding the diagnosis. The clinical picture of HSP is often incomplete and renal signs can become manifest years after initial signs. When based on clinical signs only, the diagnosis of HSP can therefore be missed, and some patients risk developing silent chronic renal failure after decades without appropriate treatment. Patients can also be overdiagnosed as HSP and thus submitted to unnecessary follow-up. It is therefore important that HSP should be correctly diagnosed from the initial signs. As the finding of IgA deposits in vessel walls associated with the characteristic signs of small-vessel vasculitis is a sine qua non in the diagnosis, a skin biopsy should be performed for histological and immunofluorescence studies in cases of clinical suspicion of HSP. The systematic diagnostic use of a cutaneous biopsy should not only improve the follow-up of patients with HSP but will also allow a reliable epidemiological study of vasculitis in children and a better knowledge of the disease.

IgA nephropathy presenting clinical features of poststreptococcal glomerulonephritis

IgA nephropathy and poststreptococcal glomerulonephritis are common forms of primary glomerulonephritis in children. This paper reports a 5-year-old Omani boy who had a chance occurrence of these two different glomerular diseases. Our patient presented with clinical features of poststreptococcal glomerulonephritis and then developed recurrent macroscopic hematuria, polyarthritis, bloody diarrhea, and erythematous swelling of the penis. Renal biopsy revealed diffuse mesangial hypercellularity, with focal glomerular sclerosis, fibrous crescents, and mesangial IgA and C3 deposits, consistent with IgA nephropathy. The clinical features and differential diagnosis are outlined.

Renal biopsy 2-9 years after Henoch Schönlein purpura

Twelve children and adolescents with classical Henoch-Schönlein purpura (HSP) underwent renal biopsy 2-9 years later. The clinical course was favorable in 10 of the patients who received only supportive treatment. Two patients with a prolonged course, characterized by marked hematuria and proteinuria, were given steroids and azathioprine first and mycophenolate mofetil later. At the time of biopsy, 4 patients did not have any urinary abnormalities, 6 had hematuria and/or mild proteinuria, and 2 had proteinuria >1 g/24 h. Renal histology showed mild lesions on light microscopy. Immunohistochemistry disclosed mesangial IgA in 8 of the 12 patients. In percentages, this is a proportion of 66.6 with 95% exact confidence limits of 34.9-90.1. In this small series of selected former HSP patients, the majority had IgA nephropathy years after the initial vasculitis episode. This indicates that some patients with apparently completely healed HSP have a chronic glomerular condition that possibly means protracted disease and certainly indicates the need for careful follow-up.

Acute glomerulonephritis

Glomerulonephritis is an important cause of renal failure thought to be caused by autoimmune damage to the kidney. While each type of glomerulonephritis begins with a unique initiating stimulus, subsequent common inflammatory and fibrotic events lead to a final pathway of progressive renal damage. In this article the different forms of inflammatory glomerulonephritis and their diagnosis are discussed. In a review of therapy both immediate life saving treatment given when glomerulonephritis causes acute renal failure and more specific treatments designed to modify the underlying mechanisms of renal injury are considered.

Severely increased blood pressure in the emergency department

Patients with severely increased blood pressure often present to the emergency department. Emergency physicians evaluate and treat hypertension in various contexts, ranging from the compliant patient with well-controlled blood pressure to the asymptomatic patient with increased blood pressure to the critically ill patient with increased blood pressure and acute target-organ deterioration. Despite extensive study and national guidelines for the assessment and treatment of chronically increased blood pressure, there is no clear consensus on the acute management of patients with severely increased blood pressure. In this article, we examine the broad spectrum of disease, from the asymptomatic to critically ill patient, and the dilemma it creates for the emergency physician in deciding how and when in the process to intervene.

18. Immune-mediated renal disease

Immune-mediated renal diseases can be classified by the clinical syndromes they produce, by the attendant renal pathology, or by the dominant immune effector mechanism of renal injury. The major clinical syndromes produced by immune-mediated renal injury include the nephrotic syndrome, the nephritic syndrome, rapidly progressive glomerulonephritis, and acute renal failure. The notion of clinical syndromes facilitates diagnosis and treatment, but does not accurately define disease pathogenesis. In this summary, we discuss pathologically defined immune-mediated renal diseases under the clinical syndrome with which they are most frequently associated. There is overlap between the clinical syndromes, but the syndromes provide a useful framework. Relevant information regarding the proposed pathogenesis of disease entities is included under specific disease entities.

Progress in molecular and genetic studies of IgA nephropathy

Several new findings emerged recently from biochemical, genetic, and molecular studies of patients with IgA nephropathy. It appears that immunoglobulin A1-secreting cells of IgA nephropathy patients produce increased amounts of aberrantly glycosylated IgA1 in which the O-linked glycans in the hinge region are deficient in the content of galactose. The galactose-deficient IgA1 in the circulation is recognized by naturally occurring antibodies with anti-glycan specificity, and immune complexes are formed. These circulating immune complexes escape hepatic degradation and eventually are deposited in the kidney mesangium. Resident mesangial cells bind the IgA-containing immune complexes with the involvement of a novel IgA receptor and become activated. A familial form of IgA nephropathy has been linked to chromosome 6q22-23. Recent progress in molecular analyses of IgA nephropathy thus defines this disease as an autoimmune process with a novel IgA mesangial receptor and certain genetically determined traits.