Primary antiphospholipid syndrome: a distinct entity?

Although antiphospholipid syndrome (APS) was first fully described in the context of connective tissue diseases such as systemic lupus erythematosus (SLE), it was soon recognised that the condition can exist on its own. APS appears to represent a clinical spectrum, both in terms of APS features and the presence of other autoimmune conditions. The clinical and serological characteristics of "primary" APS (PAPS) are similar to those of secondary APS, although the clinical features are more commonly recognised in the presence of another autoimmune or inflammatory condition. Furthermore, patients with PAPS may subsequently develop SLE. It is important to identify PAPS, since it is likely to be a contributing factor for a significant proportion of patients with a variety of vascular, neurological and other conditions. It may emerge as more common than secondary APS.