Circulating autoantibodies as serological markers in the differential diagnosis of pulmonary renal syndrome

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Abstract
Pulmonary renal syndrome (lung haemorrhage and glomerulonephritis) is a fulminant condition that warrants a rapid diagnosis and treatment to prevent mortality and preserve renal functions. However, the patients frequently present with non-specific pulmonary symptoms in the early phase of the syndrome and the diagnosis is often missed. Recently, several autoantibodies have been described in association with various forms of glomerulonephritis. We evaluated the association as well as the diagnostic and the prognostic significance of these antibodies in pulmonary renal syndrome. Retrospective clinical study. University Hospital. Forty consecutive patients with biopsy verified glomerulonephritis and overt haemoptysis or pulmonary infiltrates compatible with lung haemorrhage. Analysis of proteinase 3 antineutrophil cytoplasm antibodies (PR3-ANCA), myeloperoxidase (MPO)-ANCA, antiglomerular basement membrane (GBM) and anti-entactin antibodies. Thirty-six (90%) patients possessed one or more autoantibodies. Twenty-seven (70%) patients had ANCA (PR3-ANCA, MPO-ANCA or both). The remaining positive patients (n = 9) had anti-GBM antibodies. Only two patients had anti-entactin antibodies, suggesting a poor association of these antibodies with PRS. The majority of patients with anti-GBM antibodies had a very poor clinical outcome (five irreversible renal failure; three deaths). On the other hand, despite no significant difference in clinical features or renal morphology from patients with anti-GBM antibodies, 19 patients (70%) with ANCA recovered completely following treatment. Our study demonstrated that the presence of autoantibodies is a predominant feature of PRS and that the type of immunologic injury is of paramount importance in determining the course of illness in this syndrome. Analysis of the aforementioned antibodies can help in an early differential diagnosis and thus, in better management of PRS.