Angiotensin II and post-streptococcal glomerulonephritis.

BACKGROUND: Post-streptococcal glomerulonephritis (PSGN) is a consequence of the infection by group A beta-hemolytic streptococcus. During this infection, various immunological processes generated by streptococcal antigens are triggered, such as the induction of antibodies and immune complexes. This activation of the immune system involves both innate and acquired immunity. The immunological events that occur at the renal level lead to kidney damage with chronic renal failure as well as resolution of the pathological process (in most cases). Angiotensin II (Ang II) is a molecule with vasopressor and pro-inflammatory capacities, being an important factor in various inflammatory processes. During PSGN some events are defined that make Ang II conceivable as a molecule involved in the inflammatory processes during the disease. CONCLUSION: This review is focused on defining which reported events would be related to the presence of this hormone in PSGN.

A rare case of Immunoglobulin A dominant post-infectious glomerulonephritis (IgA PIGN) in a young patient.

BACKGROUND: Immunoglobulin A dominant postinfectious glomerulonephritis (IgA PIGN) is a unique medical entity that is rare in the paediatric population. It usually presents with severe renal failure, heavy proteinuria, hypertension, and hypocomplementemia and frequently has an unfavourable prognosis. IgA PIGN generally occurs in association with staphylococcal infections and diabetes mellitus in adult patients. Other pathogens include Escherichia coli and Streptococcus sp. Immunofluorescence studies of kidney biopsy samples show IgA as dominant or codominant antibody. CASE PRESENTATION: We encountered a 3-year-old girl with IgA PIGN presenting with acute renal failure, oedema, hypertension, and heavy proteinuria of 7955 mg/g creatinine. Renal biopsy specimens showed diffuse glomerular endocapillary hypercellularity with prominent neutrophil and monocyte infiltration on light microscopy. Strong deposits of IgA and C3 were observed along the glomerular basement membranes and the mesangium by immunofluorescence microscopy, and electron microscopy revealed the presence of subepithelial humps. The patient was managed with steroid (and probatory antibiotic) therapy and is now undergoing follow-up, with a significant improvement 6 months after the initial presentation (glomerular filtration rate (GFR) and cystatin C clearance rate of 165 ml/min/1.73m2 and 106 ml/min/1.73m2, respectively). No signs of bacterial infection were detectable. CONCLUSION: This variant of IgA PIGN must be distinguished from other clinical entities, especially IgA nephropathy (mesangial IgA deposits) and postinfectious glomerulonephritis (C3, IgG and occasional IgM capillary loop deposits with or without mesangial distribution), since patients with IgA PIGN may require steroid treatment in addition to antibiotic therapy. Differential diagnosis should also include C3 glomerulopathy. IgA PIGN is a recently identified disease entity that generally manifests in adult patients with both IgA and C3 mesangial and glomerular capillary wall deposits. We present a biopsy-proven case of IgA PIGN that manifested in a patient at an exceptionally young age and that has had a good clinical outcome. To the best of our knowledge, this is the youngest IgA PIGN patient reported thus far.

Thrombotic microangiopathy with transiently positive direct Coombs test in an adult with poststreptococcal acute glomerulonephritis: a case report.

BACKGROUND: To date, a few case reports have described the association between poststreptococcal acute glomerulonephritis (PSAGN) and hemolytic anemia/thrombocytopenia, both with or without a pathology similar to that of thrombotic microangiopathy (TMA). However, the detailed mechanism leading to the complication of TMA in PSAGN patients remains to be clarified. In contrast, infection with neuraminidase-producing Streptococcus pneumoniae is a well-known cause of TMA, and it has been reported that transient positivity of the direct Coombs test is observed in up to 90% of such patients. CASE PRESENTATION: A 44-year-old man was hospitalized for acute nephritic syndrome 3 weeks after developing pharyngitis. PSAGN was suspected owing to a low complement C3, increased antistreptolysin-O and serum creatinine (5.46 mg/dL), and hematuria/proteinuria. The throat antigen test for group A Streptococcus was positive. He developed hemolytic anemia with thrombocytopenia from hospital day 9. TMA was suspected owing to minimal coagulation abnormalities. ADAMTS-13 activity was normal, whereas the direct Coombs test was transiently positive. Renal biopsy demonstrated glomerular endocapillary proliferation without crescents, but with severe tubulitis and peritubular capillaritis on light microscopy. Immunofluorescence demonstrated C3 deposition along the glomerular capillary walls, and many subepithelial humps were observed on electron microscopy. The deposition of nephritis-associated plasmin receptor (NAPlr), a nephritogenic protein of Streptococcus pyogenes, was observed only in glomeruli. Thus, the histological diagnosis was typical PSAGN, but with atypical severe tubulointerstitial lesions. A positive direct Coombs test is often observed in pneumococcal TMA patients, which is attributed to the exposure of Thomsen-Friedenreich (T) antigen by neuraminidase. As Streptococcus pyogenes is one of the neuraminidase-producing bacteria other than Streptococcus pneumoniae, T-antigen exposure was analyzed in the renal tissue of this patient using labelled peanut lectin as a probe, which has strong and specific binding affinity for T-antigen. Exposure of T-antigen was found on tubular epithelial cells and small vessels in the tubulointerstitial area, but not in the glomeruli of this patient. CONCLUSION: These findings suggest that 2 pathogenic proteins of Streptococcus pyogenes, i.e., NAPlr and neuraminidase, induced glomerular lesions of PSAGN and tubulointerstitial inflammation with TMA, respectively, resulting in severe acute kidney injury in this patient.

Hypocomplementemia (C3) as an independent predictor for children with acute post-streptococcal glomerulonephritis: a long-term observation.

OBJECTIVE: The aim of this study was to examine the altering patterns in clinical characteristics and severity of acute post-streptococcal glomerulonephritis (APSGN) in children. PATIENTS AND METHODS: We analyzed the medical records of 119 children who were diagnosed with APSGN from 1987 to 2018, retrospectively. The patients were divided into two groups: Group I (n=72, before 1998) and Group II (n=47, after 1998). Clinical, radiologic, and laboratory findings were compared between the two groups. RESULTS: The clinical manifestations, including vomiting (20.8% vs. 4.3%, p=0.014), oliguria (40.3% vs. 19.1%, p=0.016), and generalized edema (86.1% vs. 63.8%, p=0.005), were statistically less frequent since 1998. Pulmonary edema on chest X-ray (22.7% vs. 4.4%, p=0.014) was less frequent in Group II than in Group I. The level of BUN (23.3±19.3 vs. 18.8±11.2, p=0.009) was lower in Group II than in Group I, while that of creatinine was not significantly different between the two groups. C3 level was an independent factor for predicting the development of edema (odds ratio [OR]: 1.034, 95% CI: 1.010-1.060, p=0.006) and acute nephritic symptoms (≥2) (OR: 0.974, 95% CI: 0.952-0996, p=0.020). It was also negatively correlated with an increasing number of acute nephritic symptoms, including oliguria and edema, in patients with APSGN (R=-0.182, p=0.048). CONCLUSIONS: This study demonstrated that APSGN had favorable clinical manifestations and severity over the past 30 years. The monitoring of C3 levels can be used to assess the disease severity and risk of complications, including edema and oliguria, which are decreasing in South Korean children.

Latency, Anti-Bacterial Resistance Pattern, and Bacterial Infection-Related Glomerulonephritis.

BACKGROUND AND OBJECTIVES: Bacterial infection-related GN occurs concurrent to or after known or unknown infections. It is important to understand the clinical implications of the bacterial isolates, antimicrobial resistance patterns, and effect of latency-based classification on kidney and patient outcomes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In total, 501 consecutive adults diagnosed with bacterial infection-related GN between 2005 and 2017 were included from a biopsy registry of 15,545 patients at a single center in South India, and follow-up data were collected from electronic medical records until December 2019. Latency was defined as time between resolution of infection and onset of GN, which was classified as parainfectious, peri-infectious, or postinfectious GN. Longitudinal kidney and patient outcomes were studied. RESULTS: The mean age of the cohort was 40 (± 15) years, 6% were above 65 years, and 330 (66%) were men. Diabetes was present in 93 (19%) patients. Seventy percent (353 of 501) of patients had known infections, with the median latent period for parainfectious (115 of 353, 33%), peri-infectious (97 of 353, 27%), and postinfectious (141 of 353, 40%) GN being 0, 5 (4-7), and 15 (10-31) days, respectively. The most common predisposing organism was Streptococcus pyogenes (137 of 353, 39%). Drug-resistant nonstreptococcal bacteria were methicillin-resistant Staphylococcus aureus (25%, four of 16), extended-spectrum ß-lactamases (20%, 12 of 59), and carbapenem-resistant organisms (10%, six of 59). Twenty of 22 (91%) of the drug-resistant organisms were isolated from the parainfectious group. The most common site of infection was skin in peri- (23 of 97, 24%) and postinfectious GN (61 of 141, 43%), and urinary tract in parainfectious GN (35 of 115, 30%). Of 321 patients with >3 months of follow-up, 48 (15%) developed kidney failure over a median period of 10 (2-37) months and 14 (4%) died. Parainfectious GN, eGFR<30 ml/min per 1.73 m2, moderate-to-severe interstitial fibrosis and tubular atrophy, and nontreatment with renin-angiotensin system blockers were significant risk factors for progression to kidney failure by a Cox proportional-hazards model. CONCLUSIONS: Along with clinical and histologic predictors, parainfectious GN caused predominantly by nonstreptococcal and drug-resistant bacterial infections was associated with poor kidney prognosis.

Autoimmunity in Acute Poststreptococcal GN: A Neglected Aspect of the Disease.

Acute poststreptococcal GN (APSGN) is the prototype of immune complex GN and is associated with manifestations of autoimmune reactivity that have been neglected as epiphenomena. Recently, studies have demonstrated transient antifactor B autoantibodies that activate the alternative complement pathway, bringing self-immunity to a central position in the pathogenesis of APSGN. Therefore, examining other manifestations of autoimmunity that have been reported in association with poststreptococcal GN is of interest. This article reviews the renal and extrarenal manifestations of autoimmune reactivity in APSGN and considers their potential relevance in modifying the usually benign clinical course of the disease. It also discusses related aspects of the nephritogenic antigens, complement activation, and genetic elements associated with immune reactivity and their potential relevance to the familial incidence of the disease.

Factors Affecting the Progression of Infection-Related Glomerulonephritis to Chronic Kidney Disease.

Acute glomerulonephritis (AGN) triggered by infection is still one of the major causes of acute kidney injury. During the previous two decades, there has been a major paradigm shift in the epidemiology of AGN. The incidence of poststreptococcal acute glomerulonephritis (PSAGN), which develops after the cure of group A Streptococcus infection in children has decreased, whereas adult AGN cases have been increasing, and those associated with nonstreptococcal infections, particularly infections by Staphylococcus, are now as common as PSAGN. In adult AGN patients, particularly older patients with comorbidities, infections are usually ongoing at the time when glomerulonephritis is diagnosed; thus, the term "infection-related glomerulonephritis (IRGN)" has recently been popularly used instead of "post-infectious AGN". The prognosis of children with PSAGN is generally considered excellent compared with that of adult IRGN cases. However, long-term epidemiological analysis demonstrated that an episode of PSAGN in childhood is a strong risk factor for chronic kidney disease (CKD), even after the complete remission of PSAGN. Although the precise mechanism of the transition from IRGN to CKD remains unknown, its clarification is important as it will lead to the prevention of CKD. In this review, we therefore focus on the possible factors that may contribute to the progression of IRGN into CKD. Four factors, namely, persistent infection, genetic background of the host's complement system, tubulointerstitial changes, and pre-existing histological damage, are discussed.

Atypical anti-glomerular basement membrane disease complicated by methicillin-susceptible Staphylococcus aureus infection-related rapidly progressive glomerulonephritis: a case report and literature review.

Atypical anti-glomerular basement membrane (GBM) disease, which is characterized by low levels of or negativity for anti-GBM antibodies in circulation but positivity in the kidney, has been recognized in this decade. However, a therapeutic strategy has not been established to date because its outcome is better than that of classic anti-GBM disease. This case report and literature review highlight atypical anti-GBM disease in infection-related rapidly progressive glomerulonephritis. A 72-year-old Japanese man diagnosed with methicillin-susceptible Staphylococcus aureus (MSSA)-induced vertebral osteomyelitis experienced for 2 months was referred to our hospital because of renal insufficiency. He developed rapidly progressive glomerulonephritis with a serum creatinine level of 6.8 mg/dL, C-reactive protein level of 9.7 mg/dL, urinary protein-to-creatinine ratio of 3.37 g/gCr, and gross hematuria. The serum anti-GBM antibody concentration was 3.5 U/mL, which was slightly above the normal range (< 3.0 U/mL). Conservative treatment, mainly with antibiotics, improved the symptoms and renal function. The serum anti-GBM antibody concentration peaked at 4.0 U/mL on day 7 and decreased to an undetectable range at the end of eight-week antibiotic therapy. This is the first case report describing the presentation and disappearance of serum anti-GBM antibody in a patient with MSSA infection. Conservative treatment may be effective for patients with atypical anti-GBM disease complicated by infectious diseases.

Glomerulonefritis aguda postinfecciosa por Streptococcus equi en paciente pediátrico / Acute post infectious glomerulonephritis by Streptococcus equi in a pediatric patient

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Poststreptococcal acute glomerulonephritis in a girl with renal cell carcinoma: possible pathophysiological association.

The severity of the poststreptococcal acute glomerulonephritis is considered to be modulated by the immune response of each individual, although there had been few reports regarding specific factors. Renal cell carcinoma is a cancer frequently associated with paraneoplastic syndrome, characterized by fever, leukocytosis, elevated cytokines, and elevated hormone levels. All of these symptoms resolve after tumor resection. A girl with renal cell carcinoma developed renal failure rapidly, which resolved promptly right after nephrectomy for the carcinoma. She was diagnosed as having poststreptococcal acute glomerulonephritis according to the results of pathological and serological examinations. In addition, elevated serum interleukin-6 level before the surgery was detected. Six and a half years after the diagnosis, the patient's renal function was within normal range and she was tumor free. Because of the quick resolution of her renal dysfunction after the nephrectomy, paraneoplastic syndrome induced by renal cell carcinoma seemed to play a key role in the accentuation of poststreptococcal acute glomerulonephritis.

Clinicopathological profile and outcomes of infection-related glomerulonephritis in adults.

INTRODUCTION: Infection-related glomerulonephritis (IRGN) is an example of immune-mediated glomerular injury, with changing profile over the years. We analyzed the clinicopathological profile of IRGN from a single center. MATERIALS AND METHODS: Adult renal biopsies between July 2018 and January 2020 were screened, and biopsies with IRGN were included. The demographic, clinical, and laboratory data up to 6 months were analyzed. RESULTS: 27 patients were included, with 63% having evidence of current/recent infection, Staphylococcus and Streptococcus being most common (29.4%). The mean eGFR at presentation was 16.7 mL/min/1.73m2, with crescents in 70.4% of cases. 59.3% required dialysis, and 40.7% received steroids. Complete recovery was seen in 84.6%, while 11.1% developed chronic kidney disease, and 3.7% progressed to end-stage renal disease. Persistent proteinuria, hematuria, and hypertension at 6 months were seen in 11.1, 7.4, and 3.7%, respectively. There was significant negative correlation between renal recovery and history of diabetes, interstitial fibrosis and tubular atrophy (IFTA), glomerulosclerosis, and IgA deposits. There was no significant impact of steroid use on outcome. CONCLUSION: IRGN can have an aggressive course in adults, with renal recovery continuing beyond 3 months. IFTA, glomerulosclerosis, IgA deposits, and history of DM are significant negative predictors of clinical outcome, and there is no proven benefit of steroids.

[Infection-related glomerulonephritis: the new face of an old disease].

In the last decades there have been important changes in the epidemiology and natural history of bacterial infection-related glomerulonephritides. Once defined as an infancy-onset acute nephritic syndrome following a streptococcal infection, and characterized by a relative benign course, infection-related glomerulonephritis nowadays also affects the adult population, particularly the elderly and the chronically ill. The infectious agents and infection sites have become more diversified, and the prognosis is burdened by a higher rate of mortality, chronic kidney disease, end-stage renal disease and acute overload complications. In this review we highlight the main clinical features of infection-related glomerulonephritis, offering an insight into its pathogenesis and the elements that allow an appropriate differential diagnosis. We also address the uncertainties around the role of immunosuppression in its therapeutic management.

Pathogen-induced tissue-resident memory TH17 (TRM17) cells amplify autoimmune kidney disease.

Although it is well established that microbial infections predispose to autoimmune diseases, the underlying mechanisms remain poorly understood. After infection, tissue-resident memory T (TRM) cells persist in peripheral organs and provide immune protection against reinfection. However, whether TRM cells participate in responses unrelated to the primary infection, such as autoimmune inflammation, is unknown. By using high-dimensional single-cell analysis, we identified CD4+ TRM cells with a TH17 signature (termed TRM17 cells) in kidneys of patients with ANCA-associated glomerulonephritis. Experimental models demonstrated that renal TRM17 cells were induced by pathogens infecting the kidney, such as Staphylococcus aureus, Candida albicans, and uropathogenic Escherichia coli, and persisted after the clearance of infections. Upon induction of experimental glomerulonephritis, these kidney TRM17 cells rapidly responded to local proinflammatory cytokines by producing IL-17A and thereby exacerbate renal pathology. Thus, our data show that pathogen-induced TRM17 cells have a previously unrecognized function in aggravating autoimmune disease.

Poststreptococcal acute glomerulonephritis can be a risk factor for accelerating kidney dysfunction in Alport syndrome: a case experience.

Alport syndrome (AS) is a progressive kidney disease. Male cases with X-linked AS (XLAS) are reported to develop end-stage kidney disease (ESKD) at the age of around 20-30 years. One risk factor for developing ESKD at a young age is a genotype of having truncating variants in the COL4A5 gene. However, to date, other such factors have remained unclear. Here, we describe a 15-year-old Japanese boy with XLAS who had a missense variant in the COL4A5 gene. He presented with gross hematuria, severe proteinuria, oliguria, systemic edema, body weight gain, and hypertension after pharyngitis. Blood examination showed kidney dysfunction, hypocomplementemia, and elevated antistreptolysin-O level. We diagnosed him with poststreptococcal acute glomerulonephritis (PSAGN) and he was stopped treatment by lisinopril, and received supportive treatment. However, he showed an unusual clinical course for PSAGN and, consequently, developed ESKD 15 months after the onset of PSAGN without recovery from the kidney dysfunction. This case showed that the onset of PSAGN can be a risk factor for AS patients to develop ESKD at a young age.

A case of glomerulonephritis caused by brucellosis.

Brucellosis is the most common zoonosis in the world. It can affect several organs or systems, of which the genitourinary is the second most common after the musculoskeletal. Renal involvement in brucellosis takes the form of IgA nephropathy, interstitial nephritis, pyelonephritis, mixed cryoglobulinemia and kidney failure. While the agent can be isolated in urine, renal involvement is rare (<1%). We describe a case of a 58-year-old man presenting with oedema and proteinuria. Brucellosis is considered an aetiological factor in patients presenting with glomerulonephritis in endemic regions. Brucellosis serology may assist with the early diagnosis of this rare complication.

Postinfectious Glomerulonephritis.

Postinfectious glomerulonephritis continues to be the most common cause of acute glomerulonephritis in children. Although in the past it was considered to be mainly a complication of streptococcal infections, today it is well known that infection with many other pathogens may trigger an immune response that results in glomerular injury. Most children with postinfectious glomerulonephritis have an excellent prognosis with complete recovery of renal function and no recurrence. This article summarizes the history, presentation, evaluation, differential diagnosis, and management of children with postinfectious glomerulonephritis. [Pediatr Ann. 2020;49(6):e273-e277.].

Hansen's disease with lepra reaction presenting with IgA dominant infection related glomerulonephritis.

Various renal abnormalities in leprosy have been described largely in literature but the occurrence of IgA dominant infection related glomerulonephritis in leprosy with type 2 lepra reaction has not been reported so far. We present here a 60-year-old man with a history of leprosy in the past admitted with type 2 lepra reaction, rapidly progressive glomerulonephritis with severe renal failure requiring dialysis and diagnosed to have IgA dominant infection related glomerulonephritis.

[Bartonella endocarditis associated with glomerulonephritis and neuroretinitis]. / Endocarditis por Bartonella asociada a glomerulonefritis y neurorretinitis.

Blood-culture negative endocarditis is a diagnostic challenge. Both Bartonella and Coxiella can cause it with similar clinical presentations mimicking a systemic vasculitis. The identification of the etiologic agent is essential because they differ in treatment type and duration. We present a case of blood-culture negative endocarditis caused by Bartonella henselae, associated with glomerulonephritis and neuroretinitis, with negative blood culture, positive anti-neutrophil cytoplasmic and antiproteinase 3 antibodies. The serology was positive for Bartonella with crossreactivity to Coxiella burnetti. The etiological diagnosis was achieved by polymerase chain reaction amplification and sequencing of a ribC gene fragment. The patient received antibiotic and immunosuppressive treatment followed by replacement of the aortic valve with favorable medium-term evolution.

La endocarditis bacteriana con hemocultivo negativo constituye un dilema diagnóstico. Tanto Bartonella como Coxiella pueden causarla, con presentaciones clínicas similares que pueden simular una vasculitis sistémica no infecciosa. Sin embargo, difieren en el tipo y la duración del tratamiento, por lo que es fundamental identificar el agente etiológico. Presentamos un caso de endocarditis por Bartonella henselae asociada a glomerulonefritis y neurorretinitis, con hemocultivo negativo, anticuerpos anticitoplasma de neutrófilos y antiproteinasa 3 positivos, y serología positiva para Bartonella con reacción cruzada para Coxiella burnetti. El diagnóstico etiológico fue confirmado a posteriori mediante amplificación y secuenciación parcial del gen ribC a partir de tejido de la válvula cardíaca. El paciente recibió tratamiento antibiótico e inmunosupresor seguido de recambio valvular aórtico y presentó evolución favorable.

Endocarditis por bartonella asociada a glomerulonefritis y neurorretinitis / Bartonella endocarditis associated with glomerulonephritis and neuroretinitis

La endocarditis bacteriana con hemocultivo negativo constituye un dilema diagnóstico. Tanto Bartonella como Coxiella pueden causarla, con presentaciones clínicas similares que pueden simular una vasculitis sistémica no infecciosa. Sin embargo, difieren en el tipo y la duración del tratamiento, por lo que es fundamental identificar el agente etiológico. Presentamos un caso de endocarditis por Bartonella henselae asociada a glomerulonefritis y neurorretinitis, con hemocultivo negativo, anticuerpos anticitoplasma de neutrófilos y antiproteinasa 3 positivos, y serología positiva para Bartonella con reacción cruzada para Coxiella burnetti. El diagnóstico etiológico fue confirmado a posteriori mediante amplificación y secuenciación parcial del gen ribC a partir de tejido de la válvula cardíaca. El paciente recibió tratamiento antibiótico e inmunosupresor seguido de recambio valvular aórtico y presentó evolución favorable.

Blood-culture negative endocarditis is a diagnostic challenge. Both Bartonella and Coxiella can cause it with similar clinical presentations mimicking a systemic vasculitis. The identification of the etiologic agent is essential because they differ in treatment type and duration. We present a case of blood-culture negative endocarditis caused by Bartonella henselae, associated with glomerulonephritis and neuroretinitis, with negative blood culture, positive anti-neutrophil cytoplasmic and antiproteinase 3 antibodies. The serology was positive for Bartonella with cross-reactivity to Coxiella burnetti. The etiological diagnosis was achieved by polymerase chain reaction amplification and sequencing of a ribC gene fragment. The patient received antibiotic and immunosuppressive treatment followed by replacement of the aortic valve with favorable medium-term evolution.