CYP2D7 is a cytochrome P450 pseudogene located on chromosome 22 that is highly homologous to the functional pharmacogene CYP2D6 1. However, CYP2D7 harbors a premature stop codon that prevents functional protein expression in most individuals 2. Despite early reports suggesting CYP2D7 might metabolize codeine to morphine 3, functional studies have conclusively demonstrated that CYP2D7 produces neither catalytic activity toward CYP2D6 substrates (bufuralol, dextromethorphan) nor morphine from codeine 42. When expressed, CYP2D7 protein localizes to mitochondrial rather than microsomal fractions, further supporting its non-functional status 4. The clinical significance of CYP2D7 lies primarily in its structural homology to CYP2D6; CYP2D7::CYP2D6 and CYP2D6::CYP2D7 gene conversions occur in ~2-8% of populations and can generate hybrid genes affecting CYP2D6 genotyping accuracy 56. Additionally, CYP2D7 polymorphisms (rs1800754, rs2743461) have been associated with increased coronary heart disease risk in Han Chinese populations 7. Accurate detection of CYP2D7 structural variations is essential for correct CYP2D6 phenotype classification and appropriate drug dosing recommendations 5.