Serum homocysteine, folate, and vitamin B₁₂ levels in patients with vitiligo and their potential roles as disease activity biomarkers: A systematic review and meta-analysis

Background: Hyperhomocysteinemia and folate and vitamin B₁₂ deficiencies have been reported in patients with vitiligo. Investigating the role of these conditions might shed light on the pathogenesis of vitiligo. Objective: To perform a systematic review and meta-analysis of studies assessing serum homocysteine, folate, and vitamin B₁₂ levels in vitiligo patients. Methods: Online databases were searched on May 15, 2018, to identify studies comparing serum homocysteine, folate, and vitamin B₁₂ levels between patients with vitiligo and controls. A random effects model was used. Results: Twenty-two studies involving a total of 1448 patients with vitiligo were included. Patients with vitiligo had significantly higher serum homocysteine levels (standardized mean difference [SMD] 0.550, 95% confidence interval [CI] 0.262-0.838; I² 87.3%) and lower vitamin B₁₂ levels (SMD −0.430, 95% CI −0.738 to −0.121; I² 85.3%) than controls. Serum folate levels were not significantly different between the 2 groups (SMD –0.240, 95% CI –0.592 to 0.111; I² 85.5%). A subgroup analysis revealed that these findings correlated with disease activity. Limitations: The included studies were heterogeneous. Serum homocysteine levels could be influenced by various factors. Conclusion: Patients with vitiligo have higher serum homocysteine levels and lower vitamin B₁₂ levels than individuals without vitiligo.