MTHFR and laryngotracheoesophageal cleft: Compared with that in LC patients without PVT, the incidence of some prothrombin genotypes, including the Factor V Leiden G1691A mutation, methylenetetrahydrofolate reductase (MTHFR) C677T mutation, and the prothrombin G20210A mutation, is higher in LC patients with PVT (59).