Immunoglobulin (Ig) A nephropathy and its mimics
| IgA nephropathy1,12 | Systemic IgA vasculitis1,12 | IgA-dominant postinfectious glomerulonephritis13 | Proliferative glomerulonephritis with monoclonal IgA deposits14 | |
|---|---|---|---|---|
| Clinical presentation | Varied, can present with a range of clinical syndromes: microscopic hematuria (more common than macroscopic), acute kidney injury, rapidly progressive glomerulonephritis, macroscopic hematuria with concurrent respiratory or gastrointestinal infection (ie, synpharyngitic hematuria) Involvement limited to kidneys | More common in children Extrarenal involvement (leukocytoclastic vasculitis; rash; joint pain; gastrointestinal, pulmonary, neurologic involvement) | Older adults, hypocomplementemia, acute kidney injury with hematuria and proteinuria | Rare; involvement limited to kidneys |
| Kidney biopsy | Dominant mesangial IgA staining on immunofluorescence microscopy with variable IgG staining and frequent C3 staining; chunky, irregular mesangial IgA staining on immunofluorescence Polyclonal light chain deposition with lambda more intense than kappa | Endocapillary hypercellularity, often with neutrophils, on light microscopy Dominant IgA staining with dominant or codominant C3 staining and absent or weak IgG staining; chunky, irregular mesangial IgA staining; lambda not dominant light chains on immunofluorescence microscopy Subepithelial hump-shaped immune deposits on electron microscopy | Membranoproliferative pattern on light microscopy Monotypic light chain deposition of IgA kappa more intense than lambda | |
| Pathogenesis | 4-hit model | Unclear: likely a host-pathogen interaction with superantigens stimulating host T-cell response | Unclear: rarely associated with malignancies despite monoclonal deposition of IgA | |
| Associations | Primary and secondarya distinguished by presence of associated systemic disease | Upper respiratory or gastrointestinal infection | Staphylococcus aureus infection, diabetes | Myeloma (rarely) |
↵a Common secondary: liver disease, celiac disease, inflammatory bowel disease, viral (human immunodeficiency virus, hepatitis B and C), ankylosing spondylitis, rheumatoid arthritis, systemic lupus erythematosus, psoriasis, Sjögren syndrome, tumors (lung, renal, lymphoma).
Based on information from references 1,12–14.