Vitamin D deficiency in patients with alopecia areata: A systematic review and meta-analysis

Alopecia areata (AA) is a T cell–mediated autoimmune disease that causes nonscarring hair loss.1 Some autoimmune diseases are associated with a vitamin D deficiency, including inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, and vitiligo.2,3 Previous studies that evaluated vitamin D levels in patients with AA have reached inconsistent conclusions. This study aimed to perform a systematic review and meta-analysis on the association between vitamin D levels and AA.