Risk Factors for Post-Infectious Glomerulonephritis
The primary risk factors for developing post-infectious glomerulonephritis include young age (particularly children aged 2-14 years), recent streptococcal pharyngitis or skin infection (impetigo), and exposure to nephritogenic strains of Group A beta-hemolytic streptococcus, with the disease occurring after a latent period of 1-3 weeks following the initial infection. 1, 2, 3
Age-Related Risk Factors
Children represent the highest-risk population, with peak incidence occurring between ages 2-10 years 4:
- Highest carriage rates of Group A streptococcus occur in children aged ≤14 years (10.9%), compared to 2.3% in adults aged 15-44 years and only 0.6% in those ≥45 years 1
- School-aged children (6-14 years) demonstrate the highest rates of asymptomatic streptococcal carriage, reaching up to 26% in some populations 1
- The epidemiology has shifted in recent decades, with adults (particularly elderly and immunocompromised individuals) now representing a significant proportion of cases in high-income countries 5
Infectious Risk Factors
Streptococcal Infections
Group A beta-hemolytic streptococcal infections are the classic trigger, with specific characteristics 1, 2, 3:
- Pharyngitis (strep throat) typically precedes glomerulonephritis by 1-2 weeks 6
- Skin infections (impetigo) have a longer latency period of 4-6 weeks before nephritis develops 6
- Exposure to nephritogenic strains containing specific antigens (nephritis-associated plasmin receptor [NAPlr] and streptococcal pyrogenic exotoxin B [SPeB]) increases risk 2
Non-Streptococcal Infections (Emerging Risk)
Non-streptococcal organisms are increasingly recognized as causative agents, particularly in adults 2, 5:
- Staphylococcal infections (skin, endocarditis, deep-seated infections) are now the main etiological agents in high-income countries among adults 5
- Group C and G beta-hemolytic streptococci can cause acute glomerulonephritis, though a clear causal relationship remains less established 1
Host-Related Risk Factors
Immunologic Factors
- Asymptomatic pharyngeal carriers of Group A streptococci have an extremely low risk of post-streptococcal complications 1
- Immunocompromised status increases susceptibility, particularly in adults 5
Comorbid Conditions (Adult-Specific)
Adults with certain comorbidities face higher risk and worse outcomes 5:
- Diabetes mellitus increases risk and is associated with failure to recover renal function 5
- Elderly patients demonstrate higher susceptibility and poorer prognosis 5
Environmental and Geographic Risk Factors
Socioeconomic factors significantly influence disease incidence 3:
- Poor access to clean drinking water, inadequate sanitation, and suboptimal hygiene increase risk 3
- The incidence is declining in developed countries but remains a significant public health problem in low- and middle-income countries 3
- Epidemic forms of the disease occur in settings with crowding and poor hygiene 7
Laboratory Markers Associated with Severity
While not traditional "risk factors" for developing the disease, certain laboratory findings at presentation predict worse renal outcomes 8:
- Decreased C4 complement levels (OR 11.53) strongly predict decreased GFR 8
- Hypoalbuminemia (OR 4.83) is associated with more severe renal involvement 8
- Elevated inflammatory markers (CRP >normal, OR 3.58; elevated WBC, neutrophil count, and neutrophil/lymphocyte ratio) correlate with decreased GFR 8
Clinical Pitfalls to Avoid
- Do not assume asymptomatic streptococcal carriers are at high risk—they have extremely low risk of developing post-streptococcal complications 1
- In adults presenting with infection-related glomerulonephritis, consider non-streptococcal organisms (especially Staphylococcus) as the causative agent, particularly if there is concurrent endocarditis, skin infection, or other deep-seated infection 5
- History of rheumatic fever places patients at higher risk for complications from Group A streptococcal pharyngitis, warranting more aggressive prevention strategies 1