IgA Nephropathy (Berger Disease)
IgA Nephropathy is the most common cause of glomerulonephritis worldwide. It typically presents with episodic gross hematuria following an upper respiratory or gastrointestinal infection.
1. Pathological Features
| Examination | Findings |
|---|---|
| Light Microscopy (LM) | Mesangial expansion and proliferation. |
| Immunofluorescence (IF) | IgA-based immune complex deposits in the mesangium (hallmark). |
| Electron Microscopy (EM) | Electron-dense deposits in the mesangium. |
2. Exam Must-Knows
- Clinical Timing: Unlike Post-streptococcal GN (which occurs 2–4 weeks post-infection), IgA nephropathy symptoms (hematuria) appear within days of an infection (synpharyngitic).
- Henoch-Schönlein Purpura (HSP): IgA nephropathy is considered the renal manifestation of IgA vasculitis (HSP). Look for the tetrad: purpura, arthralgia, abdominal pain, and renal involvement.
- Lab Findings: Serum C3 and C4 levels are typically normal (unlike PSGN, where C3 is low).
Pathology Board Hint: Always associate “IgA” with the “mesangium.” If the question describes a young adult with recurrent hematuria shortly after a URI, IgA nephropathy is the classic diagnosis. Remember: IgA = All ages (but common in young adults), Acute (post-URI), Abnormal (hematuria).