HLA-DRB1* alleles in Egyptian children with post-streptococcal acute glomerulonephritis

Mechanisms that potentially contribute to the development of post-streptococcal glomerulonephritis

Post-streptococcal glomerulonephritis (PSGN) is primarily associated with preceding group A streptococcal skin or throat infections, now mainly observed in economically disadvantaged communities. This condition significantly predisposes individuals to later-life chronic kidney disease and concurrent renal complications, with the elderly experiencing increased severity and less favourable outcomes. Streptococcal pyrogenic exotoxin B and nephritis-associated plasmin receptor are identified nephritogenic antigens (nephritogens). Pathogenesis of PSGN is multifactorial. It can involve the formation of antigen-antibody immune complexes, causing inflammatory damage to renal glomeruli. Deposition of circulating immune complexes or in situ formation of immune complexes in glomeruli, or both, results in glomerulonephritis. Additionally, molecular mimicry is hypothesized as a mechanism, wherein cross-reactivity between anti-streptococcal antibodies and glomerular intrinsic matrix proteins leads to glomerulonephritis. Besides, as observed in clinical studies, streptococcal inhibitor of complement, a streptococcal-secreted protein, can also be associated with PSGN. However, the interplay between these streptococcal antigens in the pathogenesis of PSGN necessitates further investigation. Despite the clinical significance of PSGN, the lack of credible animal models poses challenges in understanding the association between streptococcal antigens and the disease process. This review outlines the postulated mechanisms implicated in the development of PSGN with possible therapeutic approaches.

Autoimmunity and Infection in Glomerular Disease

The ongoing glomerular damage of infections is not limited to the most widely known form of post-streptococcal glomerulonephritis, which is today less common in the Western world; other forms of glomerulonephritis are associated with several bacterial, viral and parasitic pathogens. The mechanisms responsible range from the direct damage of glomerular cells to the formation and deposition of immunocomplexes to molecular mimicry to the secretion of superantigens. Similarly, in the course of glomerular disease, infections are more frequent than in the general population due to the loss of immunoglobulins in urine and the immunosuppressive agents used to treat the autoimmune disease that decrease the activity of the immune system. Recognizing this two-way link, understanding its pathogenetic mechanism, and identifying the most appropriate therapeutic choice are essential for the personalized management of patients. In this continuously developing field, this short review summarizes the current state of the art as support for physicians, who are increasingly involved in managing patients with glomerular disease and infections.

Childhood Nephrotic Syndrome in Africa: Epidemiology, Treatment Trends, and Outcomes

Nephrotic syndrome is a common childhood glomerular disease that is associated with massive proteinuria and edema. Children with nephrotic syndrome are at risk of chronic kidney disease, disease-related complications, and treatment-related complications. Patients with frequently relapsing disease or steroid toxicity may require newer immunosuppressive medications. However, access to these medications is limited in many African countries owing to prohibitive cost, the need for frequent therapeutic drug monitoring, and a lack of appropriate facilities. This narrative review examines the epidemiology of childhood nephrotic syndrome in Africa, including trends in treatment and patient outcomes. In most of North Africa, as well as among White and Indian populations in South Africa, the epidemiology and treatment of childhood nephrotic syndrome closely resembles that of European and North American populations. Historically, secondary causes of nephrotic syndrome (eg, quartan malaria nephropathy and hepatitis B-associated nephropathy) were predominant among Blacks in Africa. Over time, the proportion of secondary cases has decreased, along with rates of steroid resistance. However, focal segmental glomerulosclerosis increasingly has been reported among patients with steroid resistance. There is a need for consensus guidelines for the management of childhood nephrotic syndrome in Africa. Furthermore, establishing an African nephrotic syndrome registry could facilitate monitoring of disease and treatment trends, and provide opportunities for advocacy and research to improve patient outcomes.

Renal autoimmunity: The role of bacterial and viral infections, an extensive review

Autoimmunity is a process by which the loss of self-tolerance results in an immune attack against the body own tissues and organs. For autoimmunity to occur, various elements serving as triggers were described by which infections are considered one of the leading factors. In turn, renal involvement in autoimmune diseases, whether by an organ-specific attack, or as part of a systemic disease process, is well known. As bacterial and viral infections are considered to be common triggers for autoimmunity in general, we aimed to study their association with renal autoimmunity in particular. We performed an extensive search of the recent and relevant medical literature regarding renal autoimmunity syndromes such as infection-associated glomerulonephritis and vasculitis, associated with bacterial and viral infections. By utilizing PubMed and Google Scholar search engines, over 200 articles and case reports were reviewed. Among other mechanisms, direct infection of the renal parenchyma, molecular mimicry, induction of B-cells or secretion of superantigens, bacterial and viral pathogens were found to correlate with the development of renal autoimmunity. Nevertheless, this was not true for all pathogens, as some mimic autoimmune diseases and others show a surprisingly protective effect. The exact immunopathogenesis is yet to be determined, however. For conclusion, bacterial and viral infections are linked to renal autoimmunity by both direct damage and as mediators of systemic diseases. Further research particularly on the immunopathogenetic mechanisms of renal autoimmunity associated with infections is required.

Acute post-streptococcal glomerulonephritis: analysis of the pathogenesis

Increasing evidence supports a central role of the immune system in acute post streptococcal glomerulonephritis (APSGN), but the current view of how streptococcal biology affects immunity, and vice versa, remains to be clarified. Renal glomerular immune complex deposition is critical in the initiation of APSGN; however, mechanisms previous to immune complex formation could modulate the initiation and the progression of the disease. Initial and late renal events involved in the nephritis can also be related to host factors and streptococcal factors. In this review we describe the mechanisms reported for the APSGN pathogenesis, the interactions of streptococcal products with renal cells and leukocytes, the possible effects of different nephritogenic antigens in the renal environment and the possibility that APSGN is not just due to a single streptococcal antigen and its antibody; instead, kidney damage may be the result of different factors acting at the same time related to both streptococcus and host factors. Addressing these points should help us to better understand APSGN physiopathology.

Post-infectious group A streptococcal autoimmune syndromes and the heart

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges.

New trends of an old disease: the acute post infectious glomerulonephritis at the beginning of the new millenium

The association between acute renal disease and infection has been known since the mid '800s: acute post-infectious glomerulonephritis (PIGN) is a reactive immunological process against the kidney secondary to an infection, classically caused by a Streptococcus. The typical clinical presentation of PIGN is an acute nephritic syndrome with macro- or microscopic hematuria, proteinuria, hypertension, edema and renal function impairment of variable degree. The histology is characterized by an intracapillary glomerular proliferation, but may rarely be associated with an extracapillary proliferation. The classical childhood form is still present nowadays, even with severe cases, in developing countries, while in the last decades it almost disappeared in industrialized countries, where post-infectious GN are often found in elderly patients with multiple comorbidities. These clinical variants are usually related to other infective agents, like Staphylococcus aureus, both methicillin resistant (MRSA) and susceptible, and may be characterized by an IgA-dominant deposition. Kidney biopsy is rarely needed, especially in the child, while in the adult or old patient a biopsy is warranted if there is an atypical presentation or evolution, like rapidly progressive renal failure, absent or delayed function recovery, persisting low C3, nephrotic range proteinuria and persisting high proteinuria. Current therapy strategies rely on culture-guided systemic antibiotics, especially in the old patient, in which MRSA are relatively frequent, support therapy and only in very selected cases on steroids. These latter cases include the rare PIGN with crescents and those with a severe interstitial inflammation.

Bacterial infection-related glomerulonephritis in adults

In the past, most cases of bacterial infection-related glomerulonephritis (IRGN) occurred in children following streptococcal upper respiratory tract or skin infections and were called postinfectious GN. Over the past 3 decades, there has been an important shift in epidemiology, bacteriology, and outcome of IRGN. A significant percentage of cases now target adults, particularly the elderly or immunocompromised. Because adult infections are often ongoing at the time of diagnosis, the term IRGN appears more appropriate. The sites of infection in adult IRGN are more heterogeneous than in children, and include the upper respiratory tract, skin, lung, heart, urinary tract, teeth/oral mucosa, and bone. In adults, the disease is more likely to be secondary to non-streptococcal infections, particularly staphylococcal infection. In contrast to the favorable course in children, a significant proportion of adults with IRGN, especially the elderly and diabetics, do not recover renal function. Whereas the pathogenesis of post-streptococcal glomerulonephritis has been studied extensively, leading to the identification of two candidate nephritogenic streptococcal antigens, glyceraldehyde-3-phosphate dehydrogenase and pyrogenic exotoxin B, few investigations have focused on IRGN caused by other bacteria. This review will address the current status of sporadic bacterial IRGN in adults.

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.

Prevalence of celiac disease in Egyptian children disputes the east-west agriculture-dependent spread of the disease

OBJECTIVES

Celiac disease (CD) seems to be a common disorder in north Africa; however, to our knowledge no data are yet available on its prevalence in Egypt. This study was undertaken to investigate the frequency of CD in Egyptian children.

PATIENTS AND METHODS

We investigated a sample of the general pediatric population (1500 individuals, 656 girls and 844 boys, age range 7 months to 18 years, median age 8.0 years) (group A); 150 children (age range 6 months to 13 years, median age 16 months) admitted for diarrhea or failure to thrive (group B); and 250 children and adolescents with type 1 diabetes (group C). The screening test was serum class A anti-transglutaminase (anti-tTG) antibody; immunoglobulin A (IgA) antiendomysium, total IgA, and IgG anti-tTG, and small bowel biopsy was performed for confirmation of diagnosis.

RESULTS

In group A, 8 of 1500 children fulfilled the criteria for CD diagnosis; the prevalence of CD was at least 1 in 187 individuals (0.53%; 95% CI 0.17%-0.89%). In group B, 7 of 150 children had CD (4.7%, 95% CI 1.4-7.9). In group C, 16 of 250 sera showed positive results to both the IgA anti-tTG and the IgA antiendomysium test (6.4%; 95% CI 3.4-9.4).

CONCLUSIONS

Celiac disease is a frequent disorder among Egyptian children, both in the general population and in at-risk groups. Therefore, our data do not support the theory of a Middle East-Europe CD prevalence gradient secondary to the pattern of agriculture spreading from the so-called Fertile Crescent.

Acute poststreptococcal glomerulonephritis: an update

PURPOSE OF REVIEW

Acute poststreptococcal glomerulonephritis, the most common form of acute glomerulonephritis in children, continues to be a major concern worldwide. This review summarizes the recent advances in the pathogenesis, host susceptibility factors, diverse clinical presentations, and treatment of the condition.

RECENT FINDINGS

Several recent advances have been made in identifying streptococcal antigens that may play a pathogenic role in acute poststreptococcal glomerulonephritis. Nephritis-associated streptococcal plasmin receptor and streptococcal pyrogenic exotoxin B are currently considered major putative nephritogens. Host susceptibility factors including HLA-DRB1*03011 have been found at a higher frequency in acute poststreptococcal glomerulonephritis patients than in healthy controls. Reversible posterior leukoencephalopathy and autoimmune hemolytic anemia are newly reported clinical associations with the disease. Studies from developing countries question whether the outcome is always benign. Treatment remains mostly conservative; however, controversy exists over the use of aggressive therapy with poor prognostic factors.

SUMMARY

Severe group A streptococcal disease including acute poststreptococcal glomerulonephritis remains a cause of morbidity and mortality in developing countries and among impoverished populations. Various reports on the diverse clinical manifestations that can be associated with the condition will aid physicians in prompt diagnosis and intervention, while studies focusing on better understanding of immunopathogenesis may facilitate vaccine development and prevention.