Goodpasture's syndrome may be caused by viral infections and/or inhalation of certain chemical substances leading to primary lung injury. Since the alveolar capillary basement membrane and glomerular basement membrane share cross-reactive antigens, secondary kidney injury can occur. The disease is characterized by hemoptysis, pulmonary infiltrates, glomerulonephritis, and the presence of anti-basement membrane antibodies in the blood and affected tissues.

bubble_chart Etiology

The exact disease cause has not been confirmed, but it is often speculated to be related to infections, particularly viral infections. There are also reports of prior exposure to gasoline or hydrocarbons before the onset of the disease. Therefore, these chemicals and/or viruses may be potential disease causes.

bubble_chart Pathogenesis

It is now widely recognized that the pathogenesis of kidney disease involves the immune response process of anti-basement membrane antibody nephritis. Certain disease-causing factors initially injure the alveolar septa and pulmonary capillary basement membrane, which then stimulates the body to produce anti-lung basement membrane antibodies. These antibodies, with the help of complement and other factors, trigger a series of immune reactions in the alveoli. Due to the presence of cross-reactive antigens between the alveolar basement membrane and the glomerular basement membrane, endogenous anti-lung basement membrane antibodies can also initiate an immune reaction with the glomerular basement membrane, leading to glomerular injury.

bubble_chart Pathological Changes

Diffuse hemorrhage is observed on the lung surface, with edema and old hemorrhage visible on the cut section. Microscopic examination reveals intra-alveolar hemorrhage, often with hemosiderin-laden macrophages in the alveolar spaces, and focal alveolar fibrous tissue proliferation. Immunofluorescence shows linear deposits of immunoglobulin and C3 along the alveolar septa and pulmonary capillary basement membranes. The renal pathological changes resemble rapidly progressive glomerulonephritis. Additionally, early-stage glomerular capillaries exhibit focal and segmental necrosis, while a characteristic feature of the late stage (third stage) is lymphocyte infiltration around the glomeruli.

Many patients have respiratory infections before the onset of the disease, followed by recurrent hemoptysis, which mostly occurs before kidney lesions, ranging from several years (up to 12 years at most) to several months. A few cases occur after nephritis. X-ray examination reveals diffuse or nodular shadows in both lungs, spreading from the hilum to the periphery, with clear apices and areas near the diaphragm. Often, one side is more severe. Some patients have no history of hemoptysis, but pulmonary hemorrhage is confirmed by hemosiderin in sputum and chest X-ray. During hemoptysis, pulmonary diffusion function declines, leading to hypoxemia, and anemia is common.

Renal manifestations: All cases present with proteinuria, red blood cells, and casts, and some may have gross hematuria. Renal function declines, but the progression varies. Some patients may develop acute renal failure within 1–2 days, while most progress to uremia over weeks to months. A few cases evolve more slowly, stabilizing at a certain level or relapsing after remission.

Serological tests: Anti-glomerular basement membrane antibody titers are elevated, while other autoantibodies are negative. Some cases show increased immunoglobulins. The concentration of anti-basement membrane antibodies does not necessarily correlate with the severity (grade III) of pulmonary or renal lesions.

bubble_chart Diagnosis

The diagnosis can be made based on recurrent hemoptysis, hematuria, X-ray findings, and positive hemosiderin-laden macrophages in sputum. If only pulmonary manifestations are present, it should be differentiated from idiopathic pulmonary hemosiderosis. The diagnosis becomes easier after renal symptoms appear, but it must be distinguished from necrotizing vasculitis with pulmonary and renal manifestations, as well as uremia accompanied by hemoptysis.

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For crescentic glomerulonephritis, a comprehensive treatment approach is adopted. Plasma exchange, combined with corticosteroids and cyclophosphamide, can clear and reduce the serum concentration of anti-glomerular basement membrane antibodies while also removing substances harmful to tissues, such as α and β complement components, thereby alleviating and improving renal and pulmonary lesions. In cases where plasma exchange and immunosuppressive therapy are ineffective, bilateral nephrectomy may be considered. For patients with significant pulmonary hemorrhage, peritoneal dialysis is preferable. After several months or more of dialysis, once anti-glomerular basement membrane antibodies disappear from the blood, kidney transplantation can be performed to avoid recurrence of nephritis in the transplanted kidney.