Differential Diagnosis of IgA Nephropathy (IgAN)

The differential diagnosis of IgAN can be organized into the following categories:

• Single Most Likely Diagnosis
  • Alport Syndrome: Although Alport syndrome is a genetic disorder affecting the type IV collagen in the glomerular basement membrane, some cases may present with IgA deposits, making it a consideration in the differential diagnosis of IgAN, especially in familial cases or those with associated hearing or ocular abnormalities.
• Other Likely Diagnoses
  • Henoch-Schönlein Purpura (HSP): HSP is a systemic vasculitis characterized by the deposition of IgA immune complexes, similar to IgAN. It often presents with purpura, arthritis, abdominal pain, and renal involvement, making it a likely diagnosis to consider.
  • Lupus Nephritis: Systemic lupus erythematosus (SLE) can present with various renal manifestations, including IgA deposition. The presence of other SLE criteria (e.g., malar rash, oral ulcers, serositis) would support this diagnosis.
  • Infectious Causes: Certain infections (e.g., streptococcal infections) can trigger IgA nephropathy. Identifying and treating the underlying infection is crucial.
• Do Not Miss Diagnoses
  • Goodpasture Syndrome: An autoimmune disease caused by antibodies against the glomerular basement membrane, which can present similarly to IgAN but requires immediate treatment to prevent rapid progression to renal failure.
  • ANCA-Associated Vasculitis: Conditions like granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) can present with renal involvement and may have IgA deposits. Missing these diagnoses could lead to severe consequences due to the aggressive nature of these diseases.
  • Post-Infectious Glomerulonephritis: While often caused by streptococcal infections, other pathogens can lead to a similar clinical presentation. The distinction is crucial because the treatment and prognosis differ.
• Rare Diagnoses
  • Fibrillary Glomerulonephritis: A rare condition characterized by fibrillary deposits in the glomeruli, which can sometimes be confused with IgAN due to the presence of IgA deposits.
  • Immunotactoid Glomerulopathy: Another rare glomerular disease with organized deposits that can mimic IgAN under the microscope.
  • C3 Glomerulopathy: A group of rare diseases characterized by the accumulation of complement factor C3 in the glomeruli, which might occasionally present with IgA deposits, complicating the differential diagnosis.

Each of these diagnoses has distinct clinical, laboratory, and histopathological features that can help in differentiating them from IgAN. A thorough diagnostic workup, including renal biopsy, serological tests, and clinical evaluation, is essential for accurate diagnosis and appropriate management.