Postinfectious Glomerulonephritis Lecture

Acute Poststreptococcal Glomerulonephritis

• Prototype of postinfectious glomerulonephritis
• Affects children and adolescents, but adults can also be affected
• Over 90% of cases are preceded by streptococcal infection of the throat or skin
• Patients typically present with acute nephritis 7-12 days after a throat infection or about 3 weeks after a skin infection
• Diagnosis is based on prior microbiological culture, increasing titers of streptococcal antibodies (ASO), and low serum C3 level
• ASO titer is high in most cases that follow a throat infection, but less consistent following skin infection
• Firm evidence of streptococcal infection is found in only one-third of patients with acute glomerulonephritis
• More common in developing countries, where parasitic and viral infections are common etiological agents

Postinfectious Glomerulonephritis in Adults

• Seen increasingly in immunocompromised adults and the elderly
• Frequently linked to staphylococcal and gram-negative bacterial infections, often at multiple sites

Histological Features

• Depend on the timing of biopsy
• Characterized by the presence of electron-dense deposits (humps) on the epithelial side of the GBM
• Represent discrete deposits of IgG and C3 found by immunofluorescence along the capillary loop in sites corresponding to the humps
• Diffuse proliferation of endothelial and mesangial cells and polymorph infiltration of the glomerulus

Other Forms of Glomerulonephritis

• Often follow infections of the respiratory tract
• Involve mesangial deposits of IgA, in contrast to poststreptococcal glomerulonephritis

IgA Nephropathy (Mesangial IgA Deposition or Berger's Disease)

• Most common form of primary glomerulonephritis worldwide
• Accounts for 10% of all cases of primary glomerular disease in the USA, 20% in Europe, and 30-40% in Asia
• Affects mainly older children or young adults
• Presents typically as recurrent episodes of macroscopic haematuria occurring after an upper respiratory tract infection or, less frequently, a gastrointestinal or urinary tract infection, or strenuous exercise
• Period between infection and haematuria is short, ranging from hours to a few days
• Clinical features are variable, but biopsy findings are constant and may persist indefinitely
• Biopsy shows focal and segmental mesangial proliferation and prominent deposits of IgA in the mesangium of every glomerulus, along with complement components of the alternative pathway
• Can be considered a type of renal-limited vasculitis caused by an innate defect in IgA mucosal immunity
• Glomerular damage may result from self-aggregation of abnormal glycosylated IgA1, which interacts with mesangial cells.

Learn about postinfectious glomerulonephritis, a disease that occurs after a streptococcal infection, affecting children and adolescents, and sometimes adults. Understand the symptoms and timing of the disease.