25-Hydroxyvitamin D Concentrations in Patients with Optic Neuritis as a Clinically Isolated Syndrome and Healthy Controls

Objectives: The onset of multiple sclerosis in the majority of the cases occurs as a clinically isolated syndrome (CIS). We sought to assess serum levels of 25-hydroxyvitamin D (25-OHD) in CIS patients and healthy controls. Methods: In this cross-sectional study 40 patients (36 women and 4 men) with CIS manifesting as a single isolated optic neuritis and 40 Age- and sex-matched healthy controls (35 women and 5 men) were enrolled between late October 2010 and early March 2011. General vitamin D deficiency was defined as serum 25-OHD levels of lower than 20 ng/ml and was classified as mild (15 < 25-OHD < 20 ng/ml), moderate (8 < 25-OHD < 15 ng/ml), and severe (25- OHD < 8 ng/ml). Results: We found no difference in the median interquartile range [IQR] between CIS patients and controls (17.95 [10.40- 29.13] vs. 17.00 [12.25-31.00]; P=0.57). However, when stratified by the levels of deficiency, among CIS patients a significantly higher proportion had severe vitamin D deficiency in comparison to healthy controls (20% vs. 2.5%; P=0.034). Nevertheless, the frequency of general (62.5% vs. 60%, P=0.82), mild (25% vs. 30%, P=0.80), and moderate (17.5% vs. 27.5%, P=0.42) vitamin D deficiency were not different between the two groups. Conclusions: Our findings do not indicate any significant difference of serum 25-OHD between CIS patients and healthy controls. However, in our series severe vitamin D deficiency was more frequent among CIS patients.