urine: %DMA↓, %MMA↑, %iAs↑, tAs↑ (cases with urothelial carcinoma)urine: %DMA↓ (controls with 5,10-methylenetetrahydrofolate reductase CT or TT genotype)urine: %DMA (+) (in the control group). The gene discussed is MTHFR; the disease is urothelial carcinoma.