Introduction: Vitamin D plays a role in regulating the immune response through an immunomodulatory effect, and is probably involved in the pathophysiology of Crohn's disease (CD).

Aim: to assess vitamin D status in patients with CD as well as in healthy controls and to determine associated factors of vitamin D deficiency in patients with CD.

Methods: We conducted a prospective study over 18 months, including CD patients with age and sex matched with healthy controls. Suboptimal vitamin D status was defined by vitamin D serum level < 30 ng/ml, vitamin insufficiency by vitamin D serum level between 10 and 30 ng/ml and vitamin deficiency serum level < 10 ng/ml.

Results: We included 77 subjects (52 patients with CD and 25 controls) with mean age of 38 years± 11. Most patients and controls had suboptimal levels of vitamin D (98% and 96% respectively) including vitamin D deficiency in 75% and 67%, respectively and vitamin D insufficiency in 25% and 33%, respectively. In univariate analysis, vitamin D deficiency was associated with disease flare-up (p=0.001), anemia (p=0.002), hypo-albuminemia (p=0.002), elevated C-reactive protein (CRP) (p=0.003), Crohn's Disease Activity Index (CDAI) (p<0.001), ileal location (p=0.04) and immunosuppressive therapy (p=0.01). In multivariate analysis, only CDAI was significantly associated with vitamin D deficiency (p=0.003, OR=9.33).

Conclusion: Vitamin D deficiency is common in Tunisian CD patients as well as in controls and is associated with disease activity.