Background and aims The aim of this study was to evaluate retrospective data of Vitamin D levels in SLE patients, at the beginning of the disease and mean values during 10-years follow-up, and correlate them with severe flares frequency.

Methods We selected, from a cohort of 675 SLE patients, 112 patients who had baseline Vitamin D levels at SLE diagnosis and 68 patients with at least three evaluations of Vitamin D levels during the last 10-years follow-up. The number of severe flares (defined by the SELENA-SLEDAI flare composite index) was required for all patients. We correlated the baseline Vitamin D levels with severe flare number and with patients with three or more and less than three severe flares. We also correlated severe flares with mean Vitamin D value in the last 10-years follow-up.

Results We observed a higher number of flares in patients with low disease baseline Vitamin D levels (p=0.045). We also observed that patients with three or more flares have significant lower baseline Vitamin D levels (p=0.004). The mean Vitamin D levels in the previous 10-years of disease, were lower in patients with more severe flares, although not significant (p=0.178). However, if we divide them in two subgroups (patients with three or more and less than three severe flares), the difference is significant (p=0.044).

Conclusions Vitamin D levels at the beginning of the disease and the vitamin D burden during disease are related to the number of severe flares and so resulting in more aggressive phenotypes.