**1. Introduction**

The antiphospholipid syndrome (APS), primary or associated with certain autoimmune rheumatic diseases, especially systemic lupus erythematosus, represents prothrombotic state. Coexistence of metabolic syndrome (MetS) and autoimmune rheumatic diseases is already recognized [1, 2], while clinical significance of MetS in patients with APS has not been system‐ atically studied [3]. Recent recognition of certain pleiotropic functions of vitamin D (VitD) has enabled us to hypothesize on its role in the pathogenesis of obesity, MetS, APS, autoimmunity and thrombosis. Therefore, the aim of this review will be: (1) to clarify the possible linking role of VitD between APS and MetS, (2) to critically assess the need for estimation of VitD status in APS patients, depending on the coexistence of MetS and (3) to explore the potential therapeutic role which VitD, as an immunomodulator and anti‐thrombotic agent, could have in these patients.
