In Sweden, 535,538 individuals were hospitalized because of an autoimmune disorder between January 1964 and December 2008. Compared with the rest of the national population, the standardized incidence ratio (SIR) for pulmonary embolism in the first year after admission was 6.38. Patients with immune thrombocytopenic purpura, polyarteritis nodosa, polymyositis or dermatomyositis, or systemic lupus erythematosus were at particularly high risk (SIR 10.79, 13.26, 16.44, and 10.23, respectively). The investigators, therefore, conclude that “these [autoimmune] disorders in general should be regarded as hypercoaguable disorders”.