We found that the genetic distributions of CYP2R1, CYP27A1, and CYP27B1 genotypes aligned with Hardy–Weinberg equilibrium, and allele frequencies were generally similar to the general Polish population, though the TT genotype was significantly more common in thrombosis patients (40%) than in healthy individuals (13.6%). The gene discussed is CYP27A1; the disease is deep vein thrombosis.