Anticardiolipin antibodies in leptospirosis.

The clinical course and serology of 16 cases of leptospirosis in an area with an unusually high endemic infection rate were studied to gain further insight into the pathology of the secondary immune phase that is typical of the disease. IgG anticardiolipin antibody concentrations were measured by immunoassay and found to be increased in eight serologically confirmed cases with severe complicated disease, compared with eight patients with relatively uncomplicated leptospirosis who had IgG anticardiolipin concentrations within the control reference range. This previously unreported association suggests that leptospira may induce vascular endothelial injury in severe cases and expose crypt antigens or induce conformational change of cell surface phospholipids. Leptospirosis may provide a model for an infective origin of some cases of the antiphospholipid syndrome.