Pediatric IgA nephropathies: clinical aspects and therapeutic approaches

Comparison of clinical, pathological and long-term renal outcomes of children with Henoch-Schonlein purpura nephritis and IgA nephropathy

PURPOSE

To compare clinical, pathological, and long-term renal outcomes of children with Henoch-Schonlein purpura nephritis (HSPN) and IgA nephropathy (IgAN).

METHODS

The medical records of patients diagnosed as HSPN and IgAN during childhood were evaluated retrospectively. HSPN and IgAN groups were compared in terms of gender, age, upper respiratory infection history, blood pressure; presence of nephrotic and/or nephritic syndrome; hemoglobin level, leukocyte count, C-reactive protein (CRP), serum albumin (sAlb), creatinine, complement 3 (sC3), complement 4 (sC4) and immunoglobulin A (sIgA) levels; estimated glomerular filtration rate (eGFR) and proteinuria levels; and renal pathology findings at the onset of disease; total follow-up time; and blood pressure, eGFR and proteinuria levels at the last visit.

RESULTS

Fifty-four patients were enrolled in the study [38 (70%) HSPN and 16 (30%) IgAN]. The median follow-up time was 60.5 and 72.0 months in HSPN and IgAN groups, respectively (p > 0.05). The HSPN and IgAN groups were also not different in terms of gender, age at the onset; leukocyte count, eGFR, sC3-sC4-sIgA levels; and the presence of endocapillary, extracapillary and mesangial proliferation, tubular atrophy, interstitial fibrosis and IgA, IgM, C3 accumulation in renal tissue. Upper respiratory tract infection history was more common in children with IgAN (8/16 vs 8/38, p = 0.045). sAlb (3.96 ± 0.58 vs 4.40 ± 0.46 g/dL, p = 0.005), hemoglobin (12.1 ± 1.3 vs 13.3 ± 1.2 g/dL, p = 0.004,) and the incidence of mesangial IgG deposition (15/38 vs 11/16, p = 0.049) were lower, while CRP (16.3 ± 7.2 vs 7.8 ± 4.4 mg/L, p = 0.002) and proteinuria (72.1 ± 92.4 vs 34.2 ± 37.9 mg/m²/24 h, p = 0.041) was higher in HSPN group at the onset of disease. Proteinuria and eGFR were similar between the two groups at last visit.

CONCLUSION

Children with HSPN and IgAN have little clinical and histological differences in our population. The most prominent difference at presentation with nephritis was higher proteinuria in HSPN probably associated with inflammation due to systemic vasculitis. Long-term renal outcome was good in both HSPN and IgAN.

Steroid therapy in children with IgA nephropathy

IgA nephropathy (IgAN) is one the most common primary glomerulonephritis in children and adolescents worldwide, with 20% of children developing end-stage kidney disease (ESKD) within 20 years of diagnosis. There is a need for treatment guidelines, especially for steroids in children with primary IgAN, since the STOP-IgA trial casts doubts on the use of steroids in adults with intermediate risk. Pediatricians are prone to prescribe steroids in addition to renin-angiotensin system blockade (RASB) when proteinuria is > 0.5 g/l, eGFR deteriorates < 70 ml/min/1.73 m², or when a biopsy sample shows glomerular inflammation. Lack of randomized controlled trials (RCTs) in children with IgAN has led to an absence of consensus on the use of immunosuppressive agents in the treatment of progressive IgAN. This literature review evaluates the available evidence on steroid treatment in children with IgAN.

Assessment of the effect of mesangial hypercellularity in childhood nephropathies to the clinical and laboratory findings

AIM

To assess the relationship between mesangial hypercellularity in various childhood nephropathies and clinical and laboratory parameters.

METHODS AND PATIENTS

The reports of the renal biopsies were evaluated retrospectively. The patients with diagnosis of IgA nephropathy (isolated and Henoch-Schönlein nephritis), IgM nephropathy, or isolated mesangial proliferative glomerulonephritis were included. Each nephropathy group was divided into two subgroups according to the severity of mesangial hypercellularity as mild and severe. The biochemical data and histopathological findings of the patients were recorded.

RESULTS

When the groups were compared, it was found that the patients with IgA nephropathy had hematuria (p = 0.043) and the patients with IgM nephropathy had nephrotic syndrome more frequently than the other patients (p = 0.01). No difference was detected between the groups regarding the severity of mesangial hypercellularity. On the other hand, when the groups were evaluated within themselves, no significant association was detected between the severity of mesangial hypercellularity and clinical and laboratory parameters. It was determined that the renal biopsy was performed earlier in patients with Henoch-Schönlein nephritis compared to the other cases (p = 0.004). Compared to the isolated IgA nephropathy group, it was found that the number of cases with severe mesangial hypercellularity was higher and the level of proteinuria was more prominent in patients with Henoch-Schönlein nephritis. Additionally, when the patients with Henoch-Schönlein nephritis were evaluated, the degree of proteinuria was found to be higher in patients with severe mesangial hypercellularity compared to those of showing mild mesangial hypercellularity (p = 0.002).

CONCLUSION

It was observed that there is no direct relation between the severity of mesangial hypercellularity and clinical and laboratory findings in various childhood nephropathies. However, when Henoch-Schönlein nephritis is compared with IgA nephropathy, it was found that the severity of mesangial hypercellularity was higher in cases with Henoch-Schönlein nephritis and the level of proteinuria was more prominent in those cases. However, no difference was detected in glomerular filtration rates and biochemical data with regard to the level of mesangial hypercellularity.

Aberrant glycosylation of IgA1 is inherited in both pediatric IgA nephropathy and Henoch-Schönlein purpura nephritis

Serum galactose-deficient immunoglobulin A1 (Gd-IgA1) is an inherited risk factor for adult IgA nephropathy (IgAN). In this paper, we determined the heritability of serum Gd-IgA1 levels in children with IgAN and Henoch-Schönlein purpura nephritis (HSPN), two disorders with clinical phenotypes sharing common pathogenic mechanisms. Serum Gd-IgA1 concentrations were quantified using a Helix aspersa-lectin-based enzyme-linked immunosorbent assay. As a group, 34 children with either disorder (20 with HSPN and 14 with IgAN) had significantly higher Gd-IgA1 levels compared with 51 age- and ethnicity-matched pediatric controls. Serum levels of Gd-IgA1 were also elevated in a large fraction of 54 first-degree relatives of pediatric IgAN and HSPN patients compared with 141 unrelated healthy adult controls. A unilineal transmission of the trait was found in 17, bilineal transmission in 1, and sporadic occurrence in 5 of 23 families when both parents and the patient were analyzed. There was a significant age-, gender-, and household-adjusted heritability of serum galactose-deficient IgA1 estimated at 76% in pediatric IgAN and at 64% in HSPN patients. Thus, serum galactose-deficient IgA1 levels are highly inherited in pediatric patients with IgAN and HSPN, providing support for another shared pathogenic link between these disorders.

Familial IgA nephropathy in southeastern Kentucky

BACKGROUND

Two decades ago, pedigrees of patients with IgA nephropathy (IgAN) from Pike County, KY, USA, provided evidence for a role of genetic factors in the pathogenesis of this disorder. Subsequently additional pedigrees were described for several communities from northern Italy. Recently, we found another cluster of patients in the Clay County, KY area, about 100 miles southwest of Pike County.

AIM

The purpose of this study was to evaluate and expand the pedigrees of patients with IgAN from Clay County, KY to provide additional insight into the mechanisms of inheritance of IgAN and assess the possible influence of a founder effect on the prevalence of IgAN in the region.

METHOD

Since 1980, most patients with IgAN and their relatives in eastern KY have provided personal genealogic data. These data were used to construct pedigrees that included the patients born in Clay County. Nine of 11 patients with IgAN born in Clay County, KY, USA were members of 1 or more of 5 pedigrees, each with 3 - 11 patients with IgAN.

CONCLUSION

Our findings suggest the possibility of a low-penetrance ancestral mutation in the IgAN kindreds from Clay County.

Management of leukocytoclastic vasculitis

Leukocytoclastic vasculitis (LcV) is the most common form of vasculitis of the skin and usually results from deposition of immune complexes at the vessel wall. It presents in different forms and in association with different diseases. When IgA is the dominant immunoglobulin in immune complexes, systemic involvement is likely in both children and adults (Henoch-Schönlein purpura--HSP). LcV due to IgG- or IgM-containing immune complexes has less systemic involvement and a better prognosis than HSP. Other forms of LcV include cryoglobulinaemic, urticarial and ANCA-associated LcV as well as LcV associated with vasculopathy and coagulopathy in SCLE/SLE or in bacteraemia/sepsis. The aim of diagnostic guidelines is to determine the specific type and systemic involvement of LcV and to identify an underlying cause. Basic work-up should encompass history of drug intake and of preceding infections, biopsy with immunofluorescence, differential blood count, urine analysis and throat swabs. Therapy of immune complex LcV often does not require aggressive therapy due to a usually favourable course. It includes avoidance or treatment of eliciting agents and use of compression stockings to reduce purpura. There are no large prospective randomized controlled studies. Corticosteroids are indicated when there are signs of incipient skin necrosis. In chronic or relapsing LcV we suggest colchicine as a first-line and dapsone as a second-line therapy. Corticosteroids may reduce the incidence of severe renal insufficiency in children according to some studies, but there is no study showing such an effect in adults. Severe systemic vasculitis requires immunosuppressive strategies.

IgA nephropathy and Henoch-Schönlein purpura nephritis

PURPOSE OF REVIEW

IgA nephropathy and Henoch-Schönlein purpura nephritis are common glomerular disorders in pediatrics that can potentially progress to end-stage renal disease in some patients. This review summarizes our current understanding of the pathogenesis of these closely related conditions and discusses the rationale for development of diagnostic tests and prognostic markers. The review also presents the best data for long-term outcome, clinical markers of prognosis, and the results of randomized controlled trials.

RECENT FINDINGS

Our understanding of the defective galactosylation of O-linked glycans in the hinge region of human IgA1 and its role in the pathogenesis of IgA nephropathy and Henoch-Schönlein purpura nephritis has evolved over the past decade. This review discusses studies that suggest that demonstration of galactose-deficient IgA1 in the serum may become an important diagnostic tool for these conditions. Proteomic techniques for development of biomarkers for diagnosis and prognosis show promise. Although data from randomized controlled trials have failed to support the use of immunosuppressive agents in pediatric IgA nephropathy and Henoch-Schönlein purpura nephritis, recent data indicate that angiotensin converting enzyme inhibitor therapy is indicated for reduction of proteinuria.

SUMMARY

Childhood IgA nephropathy and Henoch-Schönlein purpura nephritis have the potential for serious morbidity, either during childhood or later in adulthood. In the future clinical tests will be used for noninvasive diagnosis and as markers for judging response to treatment, particularly in those individuals at highest risk for eventual progression to end-stage renal disease.

Electrophoretic methods for analysis of urinary polypeptides in IgA-associated renal diseases

We evaluated the utility of SDS-PAGE/Western blot and CE coupled with MS (CE-MS) for detection of urinary polypeptide biomarkers of renal disease in patients with IgA-associated glomerulonephritides. In a reference cohort of 402 patients with various renal disorders and 207 healthy controls, we defined CE-MS patterns of renal damage and IgA nephropathy (IgAN). In a blinded analysis of a separate cohort of patients with IgAN (n = 10), Henoch-Schoenlein purpura (HSP) with nephritis (n = 10), and IgA-associated glomerulonephritis due to hepatitis C virus (HCV)-induced cirrhosis (n = 9), and healthy controls (n = 12), we compared SDS-PAGE/Western blot and CE-MS against clinical urinalysis for detection of urinary proteins/polypeptides. Urinalysis indicated proteinuria for 50, 90, and 33% of patients, respectively, and for none of the healthy controls. SDS-PAGE/Western blot showed urinary polypeptides abnormality for 90, 80, and 67% of patients, respectively, and for none of the healthy controls. CE-MS indicated a Renal Damage Pattern in 80, 80, and 100 of patients, respectively, and in 17% of healthy controls, with the more specific IgAN Pattern in 90, 90, and 1%, respectively, and in none of the healthy controls. Based on differences in CE-MS patterns, the disease mechanisms may differ among various IgA-associated glomerulonephritides. These exploratory findings should be evaluated in a prospective study with contemporaneous renal biopsy and urinary testing. If validated, it may be feasible to adapt the CE-MS methodology to develop novel tests to detect renal injury at earlier stages, assess clinical manifestations, and monitor responses to therapy in patients with IgA-associated renal diseases.

Serum levels of galactose-deficient IgA in children with IgA nephropathy and Henoch-Schönlein purpura

IgA nephropathy and Henoch-Schönlein purpura nephritis (HSPN) are related diseases characterized by deposits of IgA1-containing immune complexes in the renal mesangium. Adult patients with IgA nephropathy have aberrantly glycosylated IgA1 (galactose-deficient O-linked glycans) in the circulation and renal deposits. However, IgA1 glycosylation has not been studied in pediatric patients with IgA nephropathy. Using our quantitative lectin enzyme-linked immunosorbent assay (ELISA) test, we measured serum levels of galactose-deficient IgA1 of children with IgA nephropathy and HSPN and controls. Children with IgA nephropathy and HSPN had serum levels higher than those of healthy children or renal-disease controls with C1q nephropathy. Furthermore, lectin ELISA identified patients with HSPN whose clinical course mimicked that of IgA nephropathy. In summary, pediatric patients with IgA nephropathy and HSPN have an aberrancy in the glycosylation in IgA1 O-linked glycans that is similar to that in adults with IgA nephropathy.

Urinary biomarkers of IgA nephropathy and other IgA-associated renal diseases

IgA nephropathy is the most common primary glomerulonephritis and is a frequent cause for chronic kidney disease in children and young adults. Glomerular deposition of IgA also characterizes other renal disorders, including Henoch-Schoenlein purpura nephritis and immune-complex glomerulonephritis afflicting patients with liver disease due to chronic infection with the hepatitis C virus. Several treatment options are often considered, with the goal to prevent end-stage renal failure. Unfortunately, the diagnosis currently requires an invasive procedure, a renal biopsy. Because of the inherent risks, repetitive renal biopsy is frequently foregone as a means to monitor the clinical course or response to treatment. Recent advances in the analysis of the urinary proteome suggest that the excreted polypeptides include disease-specific patterns. We review recent studies of the various techniques for the identification and validation of such urinary biomarkers of IgA-associated glomerulonephritides. Currently, capillary electrophoresis coupled with mass spectrometry (MS) offers the greatest promise. To date, it seems more likely that disease-specific urinary polypeptide biomarkers are comprised of a panel of several distinct and well-defined peptides rather than a single molecule. Even most patients in clinical remission with normal clinical testing (dipstick urinalysis and quantitative proteinuria) were correctly classified by the pattern of polypeptides identified by capillary electrophoresis coupled with MS. With confirmation and refinement, such urinary testing may provide a tool for the diagnosis and monitoring of patients with IgA-associated renal diseases that is more sensitive than current standard clinical testing and far less risky than renal biopsy.