Vitamin D and antiphospholipid syndrome.

Vitamin D (vitD) has been shown to have multiple immunomodulatory properties. Hypovitaminosis D has been described in many systemic autoimmune diseases. Antiphospholipid syndrome (APS), an autoimmune disease characterized by immune-mediated thrombosis and pregnancy loss, is a peculiar model for studying vitD, since these patients do not usually have a full-blown autoimmune disease, nor do they have particular restrictions regarding sun exposure. We assessed 25-OH vitD levels in 115 APS and 128 normal healthy donors (NHD) with the LIAISON® chemiluminescent immunoassay by DiaSorin (Italy). Median values were lower in APS patients than in NHD, with the greatest difference occurring during summertime (p < 0.01), suggesting that APS patients may be somehow prevented from vitD generation upon sun exposure. In our cohort, APS patients may have been instructed to use sunscreens in the presence of positive antinuclear antibodies (ANA). Comparing patients with positive and negative ANA, we found comparable vitD levels during the summer. By subdividing APS patients according to clinical features, thrombotic APS patients showed significantly lower levels than did pure obstetric APS patients (p < 0.01). In conclusion, our study confirms previous reports of hypovitaminosis D in APS patients, making them more similar to patients with other systemic autoimmune diseases than NHD. Hypovitaminosis D may be part of the mosaic of factors that determine autoimmunity, rather than a consequence of chronic disease and its treatment. The observation that patients with thrombotic APS, an aggressive phenotype, may be more deficient than those with exclusive obstetric manifestations fits well with the beneficial effects of vitD on thrombosis described both in vitro and in vivo. Therefore, there may be a rationale to assess the efficacy of vitD supplementation in APS patients.