This study compared serum vitamin D levels and VDR FokI (rs2228570) polymorphism between leprosy patients with and without TU, assessed their association with ulcer presence, and examined the correlation between vitamin D levels and ulcer severity.<h4>Methods</h4>This case-control study involved 82 adult leprosy patients (41 with TU, 41 without) treated at a tertiary referral hospital in Jakarta, Indonesia. The gene discussed is VDR; the disease is leprosy.