Hypocomplementemic and normocomplementemic acute nephritis in children: a comparison with respect to etiology, clinical manifestations, and glomerular morphology

Standardization of Epidemiological Surveillance of Acute Poststreptococcal Glomerulonephritis. Open Forum Infect Dis 2022;9:S57-S64. [PMID: 36128411 PMCID: PMC9474944 DOI: 10.1093/ofid/ofac346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Acute poststreptococcal glomerulonephritis (APSGN) is an immune complex-induced glomerulonephritis that develops as a sequela of streptococcal infections. This article provides guidelines for the surveillance of APSGN due to group A Streptococcus (Strep A). The primary objectives of APSGN surveillance are to monitor trends in age- and sex-specific incidence, describe the demographic and clinical characteristics of patients with APSGN, document accompanying risk factors, then monitor trends in frequency of complications, illness duration, hospitalization rates, and mortality. This document provides surveillance case definitions for APSGN, including clinical and subclinical APSGN based on clinical and laboratory evidence. It also details case classifications that can be used to differentiate between confirmed and probable cases, and it discusses the current investigations used to provide evidence of antecedent Strep A infection. The type of surveillance recommended depends on the burden of APSGN in the community and the objectives of surveillance. Strategies for minimal surveillance and enhanced surveillance of APSGN are provided. Furthermore, a discussion covers the surveillance population and additional APSGN-specific surveillance considerations such as contact testing, active follow up of cases and contacts, frequency of reporting, surveillance visits, period of surveillance, and community engagement. Finally, the document presents core data elements to be collected on case report forms, along with guidance for documenting the course and severity of APSGN.

Eculizumab as a New Treatment for Severe Acute Post-infectious Glomerulonephritis: Two Case Reports

Acute post-infections glomerulonephritis (APIGN) is a frequent cause of glomerulonephritis and represents the most common cause of acute glomerulonephritis in children. It can evolve to severe acute renal failure and chronic kidney disease or even end-stage kidney disease. The precise pathophysiological mechanisms of APIGN are still incompletely understood. The implication of the alternative complement pathway and the potential benefits of C5 blockade have been recently highlighted, in particular in the presence of a C3 Nephritic Factor (C3Nef), anti-Factor B or H autoantibodies. We report two children with severe APIGN, successfully treated with eculizumab. The first patient presented a severe form of APIGN with advanced renal failure and anuria, associated with a decreased level of C3 and an increased level of soluble C5b-9, in the presence of a C3NeF autoantibody. The second case had a severe oliguric APIGN associated with low C3 level. Kidney biopsy confirmed the diagnosis of APIGN in both cases. Eculizumab allowed full renal function recovery and the avoidance of dialysis in both cases. In conclusion, the alternative and terminal complement pathways activation might be common in PIGN, and in severe cases, eculizumab might help.

Pediatric post-streptococcal glomerulonephritis: Clinical and laboratory data

BACKGROUND

Acute post-streptococcal glomerulonephritis (APSGN) is the most common post-infectious glomerulonephritis in childhood. The aim of this study was therefore to identify the possible risk factor(s) responsible for decreased glomerular filtration rate (GFR) in APSGN.

METHODS

The data of patients followed up with a diagnosis of APSGN in the Pediatric Nephrology Clinic of Gaziantep University Hospital between October 2014 and October 2016 were retrospectively evaluated.

RESULTS

The total number of subjects was 75 (male/female, 42/33) with a mean age of 8.20 ± 3.25 years. The most common presentations were edema (86.7%), macroscopic hematuria (82.7%) and hypertension (73.3%, n = 55). On laboratory examination, 28 children (37.3%) had hypoalbuminemia, 58 (77.3%) had proteinuria, 20 (26.7%) had increased C-reactive protein (CRP), while 74 (98.7%) and 12 (16%) had decreased complement (C)3 and C4, respectively. The number of children with GFR <90 mL/min/1.73 m² was 22 (29.3%). The risk of decreased GFR was significantly higher in patients with increased CRP (P = 0.001; OR, 3.58), hypoalbuminemia (P = 0.006; OR, 4.83), and decreased C4 (P = 0.010; OR, 11.53). Additionally, white blood cell (WBC) count, neutrophil count, and neutrophil/lymphocyte ratio (NLR) were significantly higher (P = 0.02, P = 0.006, P = 0.004, respectively) in patients with low GFR.

CONCLUSIONS

Although the prognosis of APSGN in children is good, severe systemic complications and renal failure may develop during the follow-up period. Decreased C4, presence of hypoalbuminemia, and increased inflammatory markers (WBC, CRP, neutrophil count and NLR) might be possible risk factors for severity of renal involvement. Decreased C4, in particular, may be a risk factor for decreased GFR in those children.

Post-streptococcal acute glomerulonephritis in children: clinical features and pathogenesis

Post-streptococcal acute glomerulonephritis (PSAGN) is one of the most important and intriguing conditions in the discipline of pediatric nephrology. Although the eventual outcome is excellent in most cases, PSAGN remains an important cause of acute renal failure and hospitalization for children in both developed and underdeveloped areas. The purpose of this review is to describe both the typical and less common clinical features of PSAGN, to outline the changes in the epidemiology of PSAGN over the past 50 years, and to explore studies on the pathogenesis of the condition with an emphasis on the search for the elusive nephritogenic antigen.

Complement Activation in Renal Disease

Perturbation of the serum complement system in glomerulonephritis can be the result of classical pathway activation by immune complexes or of C3 activation by the C3-C5 convertase stabilized by the C3 nephritic factor. Low C3 levels can also be the result of diminished C3 synthesis and possibly, in certain circumstances, of C3 convertases deposited on capillary walls. In glomerulonephritis the complement profile is helpful in diagnosis, in following the course of therapy and in providing insights into pathogenesis. Complement profiles must be interpreted recognizing that a pattern resembling classical pathway activation can be produced by idiopathic nephrotic syndrome, that hypogammaglobulinemia can reduce Clq levels, and that a primary deficiency of factor H or I or both, will secondarily produce subnormal levels of C3 and factor B. With these caveats, the complement profiles typical of systemic lupus erythematosus, membranoproliferative glomerulonephritis, acute glomerulonephritis, acquired Cl inhibitor deficiency, and hypocomplementemic vasculitis syndrome are described.

Delay in diagnosis in poststreptococcal glomerulonephritis

OBJECTIVE

To determine the frequency and risk factors for diagnostic delays in children with poststreptococcal glomerulonephritis (PSGN).

STUDY DESIGN

We reviewed the charts of 52 children with PSGN, and identified children with a delay in diagnosis of more than 24 hours. We determined risk factors for delay in diagnosis using univariate and multivariate logistic regression.

RESULTS

17 children (33%) with PSGN had a delay in diagnosis. Delay in diagnosis occurred in 14% of children with gross hematuria as a presenting complaint and in 54% of children without gross hematuria as a presenting complaint (3.8 increased relative risk, 95% CI = 1.4 to 10; P = .02). A delay in diagnosis was more common in children with a negative infection history (P = .04). In multiple logistic regression, only the absence of gross hematuria as a presenting complaint was associated with a delay in diagnosis (P = .01). All children with a delay in diagnosis had microscopic hematuria on their initial urinalysis.

CONCLUSIONS

Delay in diagnosis is common in children with PSGN, especially if visible hematuria is not a presenting complaint. Physicians should consider the possibility of PSGN in children with symptoms that may be secondary to volume overload. A urinalysis is a helpful initial diagnostic test.

Plasma terminal complement complexes in acute poststreptococcal glomerulonephritis

In most instances of acute poststreptococcal glomerulonephritis (APSGN), activation of the complement system occurs, as reflected by decreased levels of the complement proteins C3, C5, and properdin (P). Recent studies implicate terminal complement complexes (TCC) in the pathogenesis of glomerular injury. The fluid phase TCC, SC5b-9, reflects the formation of membrane-bound C5b-9 and has been used as a clinical marker in various diseases. Plasma concentrations of SC5b-9 were measured with an enzyme immunoassay using a monoclonal antibody to a neoantigen expressed on the SC5b-9 complex in 13 children who presented with clinical and pathologic features of APSGN. SC5b-9 was significantly elevated in all plasmas obtained within 30 days after onset of clinical glomerulonephritis. Concentrations of SC5b-9 in acute plasmas were significantly higher than those of paired convalescent samples. For individual patients, as SC5b-9 concentration returned to normal there was a coincident decrease in serum creatinine concentration and urinary protein excretion, signifying clinical improvement in glomerulonephritis. Thus, TCC generation commonly occurs in the early stages of APSGN and may be of importance in the pathogenesis of the condition.

Serum terminal complement component levels in hypocomplementemic glomerulonephritides

Measurements of serum C3 through C9 are reported for patients with acute poststreptococcal glomerulonephritis (AGN), membranoproliferative glomerulonephritis type I (MPGN I), MPGN II, and MPGN III. Except in MPGN II, depressed C5 levels correlated with depressed C3 levels. In MPGN II, levels of C5 and of other terminal components were normal. In MPGN III, markedly depressed levels of C7 through C9 correlated strongly with depressed levels of C3 and C5. C6 was less severely depressed. In MPGN I, terminal component levels were less often depressed than in MPGN III and in AGN, depression of terminal components was seen only when levels of C3 and C5 were extremely low. The data indicate that late terminal components are activated in MPGN III to a greater extent than in the other nephritides despite C5 activation approximately equal in extent to that in AGN and MPGN I.

Antibody to a cryptic, solid phase C1Q antigen in membranoproliferative nephritis

IgG containing material detected in membranoproliferative nephritis (MPGN) serum with a solid phase (sp) Clq ELISA has been presumed to be immune complexes. However, in serum from 13 MPGN patients containing large amounts of spClq-binding material, sucrose density ultracentrifugation and sieve chromatography showed spClq-binding protein to sediment at 7S or cofractionate with IgG. One serum (stored for 12 years) contained, in addition, spClq-binding material sedimenting at more than 19S. Isolated MPGN IgG was shown to bind to spClq. SpClq-binding material could be totally removed from MPGN serum by absorption with BSA-anti-BSA immune precipitates, and by acid elution of the precipitates IgG binding to spClq could be recovered. F(ab')2, isolated from pepsin digested MPGN IgG, continued to bind spClq. Binding of MPGN IgG or F(ab')2 to spClq was not inhibited by 2 M NaCl. Incubation of MPGN serum with 125I Clq followed by sucrose density ultracentrifugation resulted in a peak of radioactivity at 11S, the sedimentation rate of Clq, giving evidence that material binding fluid phase Clq is not present. SpClq-binding IgG was detected in 54% of 68 MPGN patients. These results indicate that the 7S spClq-binding IgG represents antibody to a cryptic antigen revealed only when Clq fixes to a solid surface.

Complement profiles in acute post-streptococcal glomerulonephritis

It is well known that the hypocomplementemia of acute post-streptococcal glomerulonephritis (APSGN) is characterized by markedly reduced serum concentrations of C3 and moderately reduced levels of C5 and properdin (P). However, the extent of the activation of the classical pathway is not well defined and only limited data are available concerning serum concentrations of terminal components other than C5. In serial serum specimens from 14 children with APSGN, the presence and extent of C4 activation was directly assessed by measurement by rocket immunoelectrophoresis for C4 and C4 (C4d/C4 ratio). Elevated values for this ratio, indicating C4 activation, were found in 8 of 14 of the initial serum specimens, and in some patients the ratio remained elevated for several weeks. In contrast, the serum C4 level was low in only 1 specimen (the specimen with the highest C4d/C4 ratio). However, in 10 patients C4 concentrations within the normal range rose in serial serum specimens. Serum C2 concentrations were depressed in the initial specimens from 5 patients. The concentrations of 13 other complement component and control proteins were also measured in these specimens. Levels of terminal components, other than C5, in the initial serum specimens were normal except for depressed C8 in 3 of 13 patients and depressed C6 in 1 of 14. Of these 4 individuals, 3 had the lowest C3 levels in the study. It is concluded that the classical complement pathway is frequently activated in patients with APSGN early in the condition and that subtle abnormalities in C6 and C8 levels occasionally occur.

Glomerular membranopathy in adolescents with insulin-dependent diabetes

Kidney biopsy specimens from 15 patients ranging in age from 11 to 19 years with two- to 14-year histories of insulin-dependent diabetes mellitus were evaluated electron microscopically. Although the mean duration of disease was only eight years, the glomerular basement membrane (GBM) in these patients showed a variety of alterations typical of insulin-dependent diabetes mellitus. Saccular glomerular microaneurysms, previously little recognized, were seen in six of the specimens. These lesions, always associated with breaks in the paramesangial BM, were morphologically distinct from the ectatic capillary loops and glomerular capillary aneurysms described previously in diabetic glomerulopathy. All of the patients with such aneurysms also had other severe GBM alterations. Lytic or mechanical injury to the structurally and biochemically altered diabetic GBM may be responsible for the formation of microaneurysms.

Henoch-Schönlein syndrome and selective IgA deficiency

A 9 year old girl presented with clinical manifestations of Henoch-Schönlein syndrome and macroscopic haematuria. Laboratory investigations showed selective IgA deficiency and renal biopsy showed mesangial proliferative glomerulonephritis with diffuse granular deposits of C3 on immunofluorescence. IgA deposits were absent.

Inherited complement component deficiencies in membranoproliferative glomerulonephritis

Anecdotal reports of complement component deficiencies in patients with immune complex disease led to a systematic study of the levels of seven complement components in serum specimens from 178 patients with glomerulonephritis and 163 normal subjects. Deficiencies were found with significantly higher frequency (22.7%) among 44 patients with membranoproliferative glomerulonephritis (MPGN) types I and III, than among the normal subjects (6.7%, P less than 0.002) or among 134 patients with other glomerulonephritides (5.2%, P less than 0.001). The component deficiencies in MPGN were partial in nine patients and subtotal in one. They could not be ascribed to acquired hypocomplementemia or to a nephrotic syndrome. They were present over long periods, were found in family members, and involved C2, C3, factor B, C6, C7, and C8. Six were presumably the result of null structural genes, two were associated with a structurally abnormal component, and two were of unknown cause. The results give evidence that partial deficiency of one or more complement components is a factor predisposing to MPGN.

Glomerular deposition of complement-control proteins in acute and chronic glomerulonephritis

Acute poststreptococcal glomerulonephritis (AGN) differed from membranoproliferative glomerulonephritis (MPGN) and lupus nephritis (SLE) in that two of the proteins that control the C3b-dependent convertase, beta 1H and the C3bC4b-inactivator cofactor (C3bC4bICo), were frequently absent from the glomerular deposits. In addition, factor B was distributed with C3 in the capillary walls in hypocomplementemic AGN patients. From this, it can be assumed that C3bBb is in the deposits, uninhibited by control proteins as would be predicted for alternative pathway activation. Factor B could not be found in normocomplementemic AGN, was rarely present in MPGN, but was usually present in SLE, most often in the mesangium. In MPGN and SLE, the control proteins were nearly always present in the glomeruli in a distribution like that of C3; IN MPGN they were particularly abundant. Complement profiles indicated an occasional transient reduction in serum C4 level early in AGN. Thus, although there is occasional evidence of early classical activation in AGN, more characteristic is a long period of alternative activation. Serum levels of control proteins did not deviate greatly from normal except for reduced serum beta 1H levels in MPGN type I.

Unusual ultrastructural features in a case of acute diffuse proliferative glomerulonephritis

A case consistent with recurrent acute poststreptococcal glomerulonephritis but with atypical features is described. Light microscopy revealed a diffuse proliferative glomerulonephritis. A spectrum of ultrastructural features, from the typical "humpy bumpy" subepithelial deposits to the apparent disappearance of the deposits within the epithelial cells, is presented. An unusual piling up of basement membrane material around the deposits is described, together with some areas showing an appearance reminiscent of membranous glomerulopathy. Resorption of the dense deposits within epithelial cells is suggested and a hypothesis advanced that the basement membrane reaction may indicate an incipient chronic immune complex lesion.

Asymptomatic hematuria and proteinuria in children: differentiating the causes

In dealing with asymptomatic hematuria or proteinuria in the pediatric population, the physician should begin with an organized, logical sequence of diagnostic steps, including careful review of the history, physical findings, and laboratory data. If serious glomerular disease is suspected (eg, presentation atypical of acute poststreptococcal glomerulonephritis, nephrotic syndrome beyond the usual age for idiopathic nephrotic syndrome of childhood, renal insufficiency, severe hypertension), biopsy is probably inevitable, and early referral to a nephrologist is urged.

Necrotizing arteritis in acute poststreptococcal glomerulonephritis: report of a recovered case

A patient with biopsy documented acute poststreptococcal glomerulonephritis and arteritis recovered completely with supportive therapy. Illness was preceded by group A streptococcal pharyngitis. At the time of presentation, serum creatinine concentration was 11.5 mg/dl. Serum cryoglobulins containing IgG and C3 were present. The first biopsy, performed during the acute illness, contained glomeruli with typical features of acute PSGN. Medium-sized arteries had extensive necrosis and leukocytic infiltration, and contained IgG, C3, and fibrin. Glomerular filtration rate returned to normal within three weeks; proteinuria cleared by three months, and microscopic hematuria by 11 months. Renal biopsy one year later showed minimal mesangial hypercellularity and no arteritis.

Post-streptococcal glomerulonephritis in African children

Streptococcal infection remains almost the sole cause of the clinical syndrome of acute glomerulonephritis in African children. Evidence for this is in elevated levels of antistreptolysin "O" (ASO) titre in 93% of 28 patients and growth of Group Abeta haemolytic streptococci from the skin and throat in 32%. Spread of infection from the skin, where lesions were present in all patients, to the throat would account for positive cultures at both sites and the frequent and vigorous antistreptolysin "O" responses. Clinical recovery occurred in most within seven days and in all within 60 days of admission. IgG and IgA, but not IgM, were increased in patients; C4 was normal in the majority and low in seven out of 24 (29%), C3 was diminished in 26 out of 28 (93%) and the mean level of C3 PA was lower than in controls. Total haemolytic complement paralleled C3 values; C3 breakdown products were not detected in any patient. Renal biopsies in seven out of 28 patients showed typical histological changes of diffuse exudative proliferative glomerulonephritis on light microscopy and fibrinogen and C3 on immunofluorescent staining. These findings suggest that events leading to glomerular damage in acute post-streptococcal nephritis in African children involve activation of both classical and alternative pathways of complement proteins and also confirm the well recognized and predictable nature of the disease, irrespective of geographical distribution.

Shunt nephritis: the nature of the serum cryoglobulins and their relation to the complement profile

The serum complement profiles of four patients with shunt nephritis indicated classical pathway activation of the complement system. The presence of mixed cryoglobulins was correlated with disease activity and the cryoglobulins were shown to be complement reactive. Antisera to two of the cryoglobulins recognized antigens of the infecting organism, and a specific bacterial antibody was identified in one cryoglobulin, giveing evidence that the cryoglobulins contained immune complexes. Bacterial antibody without detectable antigen was demonstrable in the sera indicating antibody excess. Renal morphology demonstrated mesangial proliferation and interposition with subendothelial and mesangial deposits. Parallels are drawn with active lupus nephritis.