Libman-Sacks endocarditis in the antiphospholipid syndrome: immunopathologic findings in deformed heart valves.

Objective: To examine the potential immunologic mechanism and involvement of antiphospholipid antibodies in the pathogenesis of heart valve lesions in patients with the antiphospholipid syndrome (APS).

Methods: Immunoperoxidase and immunofluorescence staining methods were used to evaluate 13 heart valve specimens derived from eight patients with the APS, either primary or secondary to systemic lupus erythematosus. Primary antibodies to human immunoglobulins, complement components, serum albumin and a monoclonal anti-idiotypic antibody to human anticardiolipin antibodies (aCL) were employed. Various tissue specimens from a patient with the APS as well as deformed and normal valves from subjects without the APS were used as controls.

Results: Linear subendothelial deposition consisting of immunoglobulins with complement components but not of a non-specific serum protein was found in deformed valves from patients with the APS. None of the control valves or tissues disclosed similar deposition. The same pattern and location of staining was obtained by the anti-idiotypic antibody to aCL. A significant amount of IgG immunoglobulins that bound to cardiolipin was eluted from a valve of a patient with secondary APS.

Conclusion: Deposits of immunoglobulins including aCL, and of complement components, are common in affected valves of patients with primary and secondary APS. Such deposits may be involved in the pathogenesis of valvular lesions.