Differential Diagnosis for Triple-Positive ANCA, Anti-GBM, and IgA Antibody in Glomerulonephritis (GN)
Single Most Likely Diagnosis
- Rapidly Progressive Glomerulonephritis (RPGN): This condition is characterized by a rapid decline in renal function, often with crescentic glomerulonephritis on biopsy. The presence of triple-positive antibodies (ANCA, anti-GBM, and IgA) can be seen in RPGN, particularly in cases with a pauci-immune pattern, which is often associated with ANCA positivity, but the coexistence of anti-GBM and IgA antibodies suggests a complex autoimmune process that can lead to RPGN.
Other Likely Diagnoses
- Goodpasture Syndrome: While classically associated with anti-GBM antibodies, some cases can also be ANCA positive, and the presence of IgA antibodies might suggest a more complex autoimmune disorder. Goodpasture Syndrome is known for causing rapidly progressive glomerulonephritis and pulmonary hemorrhage.
- Granulomatosis with Polyangiitis (GPA): This is a form of vasculitis that can affect various organs, including the kidneys, and is often associated with ANCA positivity. The presence of anti-GBM and IgA antibodies could indicate a variant or a more severe form of GPA.
- Eosinophilic Granulomatosis with Polyangiitis (EGPA): Although less commonly associated with anti-GBM antibodies, EGPA can present with ANCA positivity and renal involvement. The IgA antibodies might be part of the broader autoimmune response seen in EGPA.
Do Not Miss Diagnoses
- Wegener's Granulomatosis (now part of GPA spectrum): Similar to GPA, but with a focus on the classic triad of symptoms (respiratory tract granulomas, vasculitis, and glomerulonephritis). Missing this diagnosis could lead to delayed treatment and significant morbidity.
- Microscopic Polyangiitis (MPA): Another ANCA-associated vasculitis that can present with renal involvement and could potentially have co-existing anti-GBM and IgA antibodies, although this is less common.
Rare Diagnoses
- IgA Vasculitis (Henoch-Schönlein Purpura): While primarily associated with IgA deposition, rare cases could potentially have ANCA and anti-GBM antibodies, especially in the context of a more severe or atypical presentation.
- Mixed Cryoglobulinemia: A condition characterized by the presence of cryoglobulins (proteins that precipitate from blood at low temperatures) and can be associated with various autoimmune and infectious diseases. It might rarely present with a combination of positive antibodies, including ANCA, anti-GBM, and IgA, in the context of glomerulonephritis.