Occurrence and nature of glomerular lesions after group A streptococci infections in children

Diagnostic Challenges and Emerging Pathogeneses of Selected Glomerulopathies

Recent progress in glomerular immune complex and complement-mediated diseases have refined diagnostic categories and informed mechanistic understanding of disease development in pediatric patients. Herein, we discuss selected advances in 3 categories. First, membranous nephropathy antigens are increasingly utilized to characterize disease in pediatric patients and include phospholipase A2 receptor (PLA2R), Semaphorin 3B (Sema3B), neural epidermal growth factor-like 1 (NELL1), and protocadherin FAT1, as well as the lupus membranous-associated antigens exostosin 1/2 (EXT1/2), neural cell adhesion molecule 1 (NCAM1), and transforming growth factor beta receptor 3 (TGFBR3). Second, we examine advances in techniques for paraffin and light chain immunofluorescence (IF), including the former's function as a salvage technique and their necessity for diagnosis in adolescent cases of membranous-like glomerulopathy with masked IgG kappa deposits (MGMID) and proliferative glomerulonephritis with monotypic Ig deposits (PGNMID), respectively. Finally, progress in understanding the roles of complement in pediatric glomerular disease is reviewed, with specific attention to overlapping clinical, histologic, and genetic or functional alternative complement pathway (AP) abnormalities among C3 glomerulopathy (C3G), infection-related and post-infectious GN, "atypical" post-infectious GN, immune complex mediated membranoproliferative glomerulonephritis (IC-MPGN), and atypical hemolytic uremic syndrome (aHUS).

Acute glomerulonephritis with concurrent suspected bacterial pneumonia - is it the tip of the iceberg?

BACKGROUND

Post infectious glomerulonephritis is the most common glomerulopathy in children, occurring several weeks after nephritogenic streptococcal throat or skin infection. Reports of acute glomerulonephritis (AGN) occurring during active bacterial pneumonia in children are rare. The aim of this study was to evaluate the incidence of AGN concurrent with bacterial pneumonia in children.

METHODS

We reviewed records of all children admitted with a diagnosis of pneumonia to the pediatric department in a single tertiary medical center between January 2015 and April 2023. Patients with bacterial pneumonia and concurrent glomerulonephritis were included.

RESULTS

Eleven (0.98%) of 1,123 patients with bacterial pneumonia had concurrent AGN. All were males with a median age of 2.7 years (range 1-13). Mean time from bacterial pneumonia onset to acute glomerulonephritis symptoms was 2.7 ± 1.5 days. Five (45%) patients had evidence of pneumococcal infection. Hypertension was found in 10 (91%) patients. Mean trough eGFR was 43.5 ± 21.4 ml/min/1.73 m2 (range 11-73). Ten patients (91%) had low C3 levels. Median urinary protein-to-creatinine ratio was 2.5 mg/mg (IQR 2.15-14.75). All patients fully recovered. Microscopic hematuria was the last finding to normalize after a median of 29.5 days (IQR 17.25-38).

CONCLUSION

AGN during bacterial pneumonia may be more frequent than previously recognized. Kidney prognosis was excellent in all patients. Prospective studies are needed to evaluate the impact of this condition.

Approach to the Child with Hematuria

The causes of macroscopic and microscopic hematuria overlap; both are often caused by urinary tract infections or urethral/bladder irritation. Coexistent hypertension and proteinuria should prompt investigation for glomerular disease. The most common glomerulonephritis in children is postinfectious glomerulonephritis. In most patients, and especially with isolated microscopic hematuria, the diagnostic workup reveals no clear underlying cause. In those cases whereby a diagnosis is made, the most common causes of persistent microscopic hematuria are thin basement membrane nephropathy, immunoglobulin A nephropathy, or idiopathic hypercalciuria. Treatment and long-term prognosis varies with the underlying disease.

A rare adult case of poststreptococcal acute glomerulonephritis with a retropharyngeal abscess

Retropharyngeal abscess is an infection involving the retropharyngeal space which is posterior to the pharynx and oesophagus, and it results as a complication of a primary infection elsewhere in the head and neck including the nasopharynx, paranasal sinuses, or middle ear, which drain lymph to the retropharyngeal lymph nodes. Their lymph nodes are prominent in children and atrophy with age. Therefore, retropharyngeal abscess is most frequently encountered in children, with 75% of cases occurring before the age of 5 years, and often in the first year of life. We experienced a rare adult case of poststreptococcal acute glomerulonephritis with a retropharyngeal abscess, and conservative therapy ameliorated them. According to past reports, only one child with a retropharyngeal abscess and poststreptococcal acute glomerulonephritis has been presented at a conference to date; this is the first adult case of poststreptococcal acute glomerulonephritis with a retropharyngeal abscess. Retropharyngeal abscess can be fatal including airway compression, so it is important to remember retropharyngeal abscess in a case of poststreptococcal acute glomerulonephritis with severe symptoms of neck.

Clinico-bacteriological profile of primary pyodermas in Kashmir: a hospital-based study

Pyodermas are a common group of infectious dermatological conditions on which few studies have been conducted. This study aimed to characterise the clinical and bacteriological profile of pyodermas, and to determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infection in primary pyodermas in a dermatology outpatient department in Kashmir. Methods We conducted a hospital based cross-sectional study in the outpatient Department of Dermatology, Sexually Transmitted Diseases and Leprosy of Shri Maharaja Hari Singh Hospital, Srinagar, Jammu and Kashmir, India. Patients presenting with primary pyodermas were included in the study. A detailed history and complete physical and cutaneous examination was carried out along with microbiological testing to find aetiological microorganisms and their respectiveantimicrobial susceptibility patterns. Antimicrobial susceptibility testing, including that for methicillin resistance, was carried out by standard methods as outlined in the current Clinical and Laboratory Standards Institute guidelines. Results In total, 110 patients were included; the age of the study population ranged from 3 to 65 years (mean age 28 years); 62% were male. Poor personal hygiene was noted in 76 (69%). Furunculosis (56; 51%) was the most common clinical presentation. Staphylococcus aureus was isolated in 89 (81%) of cases, and MRSA formed 54/89 (61%) of Staphylococcus aureus isolates. All MRSA strains were sensitive to vancomycin. Conclusion The prevalence of MRSA was high in this sample of communityacquired primary pyodermas. It is therefore important to monitor the changing trends in bacterial infection and their antimicrobial susceptibility patterns and to formulate a definite antibiotic policy which may be helpful in decreasing the incidence of MRSA infection.

Work-up of hematuria

Hematuria is a common clinical manifestation of diseases affecting the urinary system. Sometimes it may not represent any underlying disease and is of no clinical significance, especially when it is transient in young adult patients. However, it may represent underlying intrinsic kidney disease or malignancy in patients, even if transient. Therefore, detection of hematuria in the appropriate clinical setting and further investigation based on the individual clinical scenario helps establish correct diagnosis and guide further management. This article discusses the etiologies and workup of hematuria.

Postinfectious glomerulonephritis

Postinfectious glomerulonephritis (PIGN) is an immunologically mediated glomerular injury triggered by an infection. Poststreptococcal glomerulonephritis (PSGN) is a classic example of PIGN with diffuse proliferative and exudative glomerular histology, dominant C3 staining and subepithelial "humps." Only the nephritogenic streptococcal infections cause PSGN and susceptibility to develop PSGN depends on both host and microbial factors. Over the last decade, two nephritogenic antigens, "nephritis-associated plasmin receptor" and "streptococcal pyrogenic exotoxin B" have been identified. PSGN is a self-limited disease, especially in children, but long-term follow-up studies indicate persistent low-grade renal abnormalities in a significant proportion of patients. PSGN continues to be a serious public health concern in third world countries, but the incidence of streptococcal infections has steadily declined in industrialized nations. PIGN in the western world is now primarily because of nonstreptococcal infections, often affecting older individuals with comorbidities such as diabetes mellitus or alcoholism, and is associated with poor outcomes. Although the acute PIGN has diffuse proliferative, focal segmental proliferative or mesangioproliferative patterns of glomerular injury, chronic or subacute infection-associated glomerulonephritis typically results in membranoproliferative appearance. PIGN has dominant C3 staining with frequent occurrence of subepithelial "humps" as well as subendothelial deposits. The immunoglobulin staining on immunofluorescence is typically weak, but immunoglobulin A-dominant PIGN is a recently defined entity often associated with staphylococcal infections. The wide spectrum of morphologic changes seen in PIGN poses a diagnostic challenge, especially if adequate clinical and serological data are lacking.

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.

A 5-year survey of biopsy proven kidney diseases in Lebanon: significant variation in prevalence of primary glomerular diseases by age, population structure and consanguinity

BACKGROUND

Differences in epidemiology of kidney disease across the Middle East may arise from variations in indication for biopsy, environmental exposure and socio-economic status. The Lebanese population is composed of different ethnicities, with distinct ancestry and religion, enabling comparison of their effect on the prevalence of kidney disease within a confined geographic setting and uniform practices. Here we report 5 years' detailed epidemiology of renal diseases, based on histological diagnosis, in a sample from three large pathology centres in Lebanon.

METHODS

Records of renal biopsies analysed at the American University of Beirut Medical Center, Hotel Dieu de France Hospital and the Institut National de Pathologie from January 2003 till December 2007 were retrospectively examined. We recorded the following data for each patient: age, gender, indication for renal biopsy and histopathological diagnosis. Religious affiliation and parents' consanguinity were recorded when feasible.

RESULTS

The mean age at renal biopsy was 36.76 ± 20 years (range 1-84). The most common diagnosis was mesangioproliferative glomerulonephritis (GN; 20%), followed by focal segmental glomerulosclerosis (13.2%). While there were no differences in age, gender or indications for biopsy among different religious affiliations, mesangioproliferative GN was significantly more frequent among Muslims (P = 0.039) and offspring of consanguineous unions (P = 0.036). On the other hand, focal segmental glomerulosclerosis was most prevalent in Christians (P < 0.001).

CONCLUSIONS

Variation in the distribution of diagnoses between Muslim and Christian groups likely reflects differences in population structure and ancestry. In particular, the increased prevalence of mesangioproliferative GN among offspring of consanguineous unions in Muslims suggests a recessive genetic component to this disease which may be identified via homozygosity mapping. These findings have important implications for formulating renal health policies and designing research studies in this population.

Glomerulonephritis and managing the risks of chronic renal disease

The rising global burden of chronic renal disease, the high cost of providing renal replacement therapies, and renal disease also being a risk factor for cardiovascular disease is increasing focus on renal disease prevention. This article focuses on the aspects of renal disease (specifically poststreptococcal glomerulonephritis [PSGN] and chronic kidney disease [CKD]) in Indigenous populations in Australia, New Zealand, Canada, and the United States that diverge from those typically seen in the general population of those countries. The spectrum of renal and many other diseases seen in Indigenous people in developed countries is similar to that seen in developing countries. Diseases like PSGN that have largely disappeared in developed countries still occur frequently in Indigenous people. CKD during the childhood years is due to congenital anomalies of the kidney and urinary tract in up to 70% of cases and occurs later in polycystic kidney disease and childhood-onset diabetes. Several risk factors for CKD in adulthood are already present in childhood.

Patterns of proteinuria and circulating immune complexes in febrile patients

Circulating immune complexes (CIC) were detected in 8 of 15 patients with fever due to non-renal infections. Elevated urinary albuMin and beta-2-microglobulin excretion rates were found during the febrile period compared to the levels two days after normalization of the temperature. No relationship could be demonstrated between CIC and the excretion rates of albumin and beta-2-microglobulin or the albumin/beta-2-microglobulin ratio. Thus we have not been able to confirm the hypothesis that the glomerular type of proteinuria is caused by immune complexes.

Acute glomerulonephritis associated with streptococcus pyogenes with concomitant spread of streptococcus constellatus in four rural families

We studied history, renal histopathology and microbiology of an epidemic of acute glomerulonephritis associated with throat infections and uncommon culture results in four neighbour families. A 40-year-old man (index patient) was referred to a university hospital for dialysis and kidney biopsy due to a suspected acute glomerulonephritis. An acute tonsillitis had preceded the condition. Penicillin treatment had been started four days before the discovery of renal failure. Throat swabs were positive for beta-hemolytic streptococci, group C (GCS). GCS were also found in throat cultures from his wife and two of their children. The bacteria were typed as Streptococcus constellatus. A third child had S. constellatus expressing Lancefield antigen group G. A neighbour and two of his children fell ill the following week with renal involvement. Throat swabs from both these children were positive for S. constellatus. His third child had erythema multiforme and S. constellatus in the throat while a fourth child had beta-hemolytic streptococci group A; Streptococcus pyogenes. Kidney biopsies on the index patient and his neighbour showed an acute diffuse prolipherative glomerulonephritis compatible with acute post-streptococcal nephritis and microbiological analysis of renal tissue revealed in both cases S. pyogenes and S. constellatus. The families had had much contact and had consumed unpasteurized milk from our index patient's farm. In four of seven persons in two additional neighbouring families S. constellatus was found in throat swabs during the same month while two persons carried Streptococcus anginosus expressing the Lancefield C antigen. In conclusion spread of S. constellatus coincided with the occurrence of four cases of acute glomerulonephritis. The two biopsied patients had both S. pyogenes and S. constellatus present in renal tissue. The epidemic either suggested that the outbreak of glomerulonephritis was due to S. pyogenes but coincided with the transmission and colonization of S. constellatus or that the S. constellatus strains were highly pathogenic or nephritogenic and that this organism can be transmitted in such cases.

Occurrence of subclinical post-streptococcal glomerulonephritis in family contacts

OBJECTIVE

There are few data in the published literature on the occurrence of subclinical post-streptococcal glomerulonephritis. In order to estimate the incidence of subclinical disease, 75 families of index cases with sporadic clinical post-streptococcal glomerulonephritis were screened for the presence of subclinical disease.

METHODS

Three hundred and seventeen family contacts were investigated 1-7 days after the admission of the index cases. The diagnosis of subclinical disease was based on the presence of abnormal urinalysis, transitory hypocomplementaemia and increased antistreptolysin O titre.

RESULTS

No cases of clinical/subclinical disease were detected among 147 parents. Abnormal urinalyses were found in 22.3% of sibling contacts. The incidence of nephritis among 170 siblings was 9.4% and the calculated ratio subclinical/clinical disease was 0.11. There were 16 siblings (9.4%) whose abnormal urinalyses could not be explained by appropriate tests; 11 of them had dysmorphic microhaematuria and significantly elevated antistreptolysin O titre.

CONCLUSIONS

Sibling contacts have increased risk for the development of clinical/subclinical post-streptococcal glomerulonephritis compared with their parents. Sibling contacts with unexplained urinary abnormalities might have subclinical nephritis in evolution; their complement levels normalized before occurrence of nephritis in index cases.

Incidental healed postinfectious glomerulonephritis: a study of 1012 renal biopsy specimens examined by electron microscopy

Glomerulonephritis (GN) characterized by immune complex deposits typical of postinfectious GN but with a paucity or absence of overt clinical symptoms and/or urinary abnormalities may occur after a group A streptococcus infection. The overall incidence of this type of subclinical GN is not known. To address this question, electron microscopy findings in 1012 consecutive renal biopsy specimens (952 native kidney, 60 transplant) examined by a single renal pathologist from August 1999 to April 2002 were retrospectively reviewed for the presence of distinct subepithelial and intramembranous deposits indicative of postinfectious GN. Such deposits were noted in 83 biopsy specimens, including 26 with a primary diagnosis of postinfectious GN (acute, persistent, or latent) and 57 in which these deposits were an incidental finding. In each of the latter 57 cases, some or all of the deposits showed partial or extensive loss of electron density typical of partially or largely resorbed deposits. A diagnosis of incidental postinfectious GN was not made in any biopsy specimen exhibiting another immune complex-related glomerular disease that could possibly account for the deposits, composing 443 of the 1012 biopsy specimens examined. Thirty of the 57 biopsy specimens with incidental postinfectious GN showed mesangial hypercellularity, although this was focal and segmental in all but 3 cases and was not accompanied by the endocapillary hypercellularity typical of acute postinfectious lesions. Immunofluorescence microscopy revealed glomerular deposits of C3 in >90% of these biopsy specimens and IgM deposits in 66%, but only rare IgG, IgA, and Cq deposits. Twenty-three (40%) of these 57 biopsy specimens exhibited diabetic nephropathy, either alone or in combination with another lesion; for perspective, only 128 (13%) of the 1012 biopsy specimens examined showed evidence of diabetic nephropathy. In summary, incidental evidence of resolving or largely healed postinfectious GN was noted in up to 10.5% of renal biopsy specimens (57 of 543, not including specimens with a primary diagnosis of an immune complex-related glomerular disease). The recognition of such lesions is potentially important in the interpretation of certain renal biopsy specimens.

Pathogenic mechanism of acute post-streptococcal glomerulonephritis

Considerable knowledge has been accumulated regarding the characteristics of acute post-streptococcal glomerulonephritis (APSGN), and many attempts have been made to identify a streptococcal factor or factors responsible for triggering this disease. However, the pathogenic mechanism behind APSGN remains largely unknown. As glomerular deposition of C3 is generally demonstrated before that of IgG in the disease process, it is likely that the inflammatory response is initiated by renal deposition of a streptococcal product, rather than by deposition of antibodies or pre-formed immune complexes. During recent years, a number of streptococcal products have been suggested to be involved in the pathogenic process. In this review, possible roles of these factors are discussed in the context of the clinical and renal findings most often demonstrated in patients with APSGN. Streptokinase was observed to be required in order to induce signs of APSGN in mice, and a number of findings suggest that the initiation of the disease may occur as a result of renal binding by certain nephritis-associated variants of this protein. However, additional factors may be required for the development of the disease.

Impetigo: an overview

This article reviews in detail the pathogenesis, clinical characteristics and management of impetigo in children. Impetigo is the most common bacterial skin infection of children. Most cases of nonbullous impetigo and all cases of bullous impetigo are caused by Staphylococcus aureus. The remainder of cases of nonbullous impetigo are due to group A beta hemolytic streptococci (GABHS). GABHS colonize the skin directly by binding to sites on fibronectin that are exposed by trauma. In contrast, S. aureus colonizes the nasal epithelium first; from this reservoir, colonization of the skin occurs. Patients with recurrent impetigo should be evaluated for carriage of S. aureus. Superficial, localized impetigo may be treated successfully in more than 90% of cases with topical application of mupirocin ointment. Impetigo that is widespread or involves deeper tissues should be treated with a beta-lactamase-resistant oral antibiotic. The choice of antibiotics is affected by the local prevalence of resistance to erythromycin among strains of S. aureus, antibiotic cost and availability, and issues of compliance.

Serum complement levels before and after the onset of acute post-streptococcal glomerulonephritis. A case report

Low serum C3, properdin, and C5 levels found in the acute stage of acute post-streptococcal glomerulonephritis (APSGN) indicate the presence of aggressive complement activation. We followed serum complement component levels in a child hospitalized with erysipelas who developed APSGN on the 2nd hospital day. Her initial serum sample, obtained prior to the clinical onset of nephritis, had a low properdin level and normal C3 and C5 levels despite the presence of C3 splitting activity. Two days later she developed gross hematuria and subsequent sera contained low C3, properdin, and C5 levels, as is usual in APSGN. These observations suggest that complement activation, predominantly through the alternative pathway, precedes the clinical onset of APSGN.

Plasma atrial natriuretic peptide and endothelin levels in acute poststreptococcal glomerulonephritis

Plasma levels of atrial natriuretic peptide (ANP) and of endothelin (ET) were significantly elevated (87.7 +/- 13.9 pg/ml and 79.7 +/- 10.8pg/ml, respectively) during the acute phase of acute poststreptococcal glomerulonephritis (APSGN). Plasma renin levels were normal, fractional excretion of sodium (FENa) was 0.5 +/- 0.1% and creatinine clearance (CCr) averaged 82.2 +/- 18.3 ml/min per 1.73 m2. In the recovery phase of the disease (n = 12), levels of ANP (23.6 +/- 6.7 pg/ml) and ET (43.1 +/- 2.4 pg/ml) fell and were not significantly different from those measured in 11 control subjects. FENa increased to 1.3 +/- 0.1% and CCr to 113.5 +/- 12.1 ml/min per 1.73 m2 (all values mean +/- standard error). ANP did not correlate with PRA, blood pressure, CCr or FENa. There was an inverse relationship between the ET level and FENa in the acute phase of the disease (r = 0.489, P < 0.05), but no significant correlation between ET and blood pressure, PRA, CCr or ANP was found. We suggest that, despite the sodium retention, the increased ANP level in APSGN indicates unresponsiveness of the kidneys to ANP; the increased ET levels may contribute to this.

Acute glomerulonephritis in children. An evolutive morphologic and immunologic study of the glomerular inflammation

This study deals with 80 children showing a clinically typical acute nephritic syndrome with proteinuria and/or hematuria, edema, and hypertension. Their ages ranged between 2 years 5 months and 16 years; 36 cases were female. In 73 cases a streptococcal infection was demonstrated; the remaining 7 cases did not show morphologic differences with the former. No previous renal disease nor familial history of nephropathies were elicited. In every case a renal biopsy was obtained in the first 60 days of clinical disease; in 46 cases a second renal biopsy was obtained sometime between 6 and 45 months since the beginning of the disease. In 3 cases the renal tissue was considered to be normal by light microscopy, immunofluorescence and electron microscopy in both the first and second biopsies. These 3 patients were not considered as cases of morphologic acute glomerulonephritis in spite of showing a typical clinical picture and they are not included in the evaluation of the glomerular inflammatory evolution. In all the remaining 77 cases C3 granular and segmentary intramembranous and mesangial dense deposits were found in the first biopsy. The second biopsy showed morphologic and immunologic normalization in 27% of the cases, slight lesions in 56% and an increase in severity in 17% of the cases.

Attack rate of poststreptococcal nephritis in families. A prospective study

Twenty-two families comprising 141 first-degree relatives (42 parents and 99 siblings) were studied prospectively after the appearance in the family of an index case with acute poststreptococcal glomerulonephritis (APSGN). There was no epidemic when the studies were conducted. Families were observed weekly for 4-6 weeks after the appearance of the index case, and at least every 6 months thereafter for 1-3 years. At each examination all members of the family gave a history and had a physical examination, urine analysis, and appropriate cultures; antistreptococcal antibody titres and serum C3 were determined. 33 parents and 95 siblings showed changes in antistreptococcal antibody titres suggestive of infection during or shortly before the period of weekly observation. Group A streptococci of various M and T types were isolated from 17 individuals in 14 families. 25 cases of clincal APSGN (including 22 index cases) and 12 cases of asymptomatic APSGN were detected. The results indicate that within families the streptococci responsible for nonepidemic APSGN are very infectious. The subclinical/clinical disease ratio (excluding index cases) was 4.0. The high attack rate (37.8%) in 77 sibling contacts at risk may indictae that susceptibility to nephritis after streptococcal infection is a familial trait.

Acute poststreptococcal glomerulonephritis mimicking Henoch-Schönlein purpura

Two children with acute glomerulonephritis, cutaneous vasculitis, and abdominal pain are reported. One child also had transient arthralgia and gastrointestinal hemorrhage. Although the clinical presentation mimicked many of the features of Henoch-Schönlein purpura, both patients had unusual variants of poststreptococcal glomerulonephritis.