Differential Diagnosis for Hemoptysis and Hematuria with Crescentic Linear Deposition of Immunoglobulins

Single Most Likely Diagnosis

• Goodpasture Syndrome: This condition is characterized by the presence of anti-glomerular basement membrane (anti-GBM) antibodies, which are responsible for the linear deposition of immunoglobulins seen on renal biopsy. It classically presents with hemoptysis and hematuria, making it the most likely diagnosis given the clinical presentation and biopsy findings.

Other Likely Diagnoses

• Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): Although GPA can present with renal involvement and pulmonary symptoms, the renal biopsy typically shows pauci-immune necrotizing glomerulonephritis rather than linear deposition of immunoglobulins. However, it can occasionally have anti-GBM antibodies, making it a consideration.
• Microscopic Polyangiitis (MPA): Similar to GPA, MPA is a form of ANCA-associated vasculitis that can present with renal and pulmonary involvement. While it more commonly shows pauci-immune glomerulonephritis, rare cases might have anti-GBM antibodies, especially in the context of "double-positive" cases (positive for both ANCA and anti-GBM antibodies).

Do Not Miss Diagnoses

• Double Antibody Positive Vasculitis: This refers to patients who are positive for both ANCA and anti-GBM antibodies. These patients can have a more severe disease course and require prompt recognition and treatment to prevent irreversible organ damage.
• Systemic Lupus Erythematosus (SLE): Although SLE more commonly presents with a "full-house" pattern on immunofluorescence (including IgG, IgA, IgM, C1q, and C3), it can occasionally have linear deposition of immunoglobulins along the glomerular basement membrane. Missing SLE could lead to delayed treatment of a potentially life-threatening condition.

Rare Diagnoses

• Alport Syndrome with Anti-GBM Antibodies: Alport syndrome is a genetic disorder affecting the type IV collagen in the glomerular basement membrane, leading to chronic kidney disease and hearing loss. Rarely, patients with Alport syndrome can develop anti-GBM antibodies, which could lead to a clinical presentation similar to Goodpasture syndrome.
• Idiopathic Crescentic Glomerulonephritis: This condition is characterized by the presence of crescents in the glomeruli without an identifiable cause. While it can present with rapid deterioration of renal function, the presence of linear immunoglobulin deposition would be unusual and suggests an underlying anti-GBM disease process.