How genetic variation was analyzed in phenytoin-induced gingival enlargement using single-nucleotide polymorphism of candidate gene CYP2C9?

Background: Phenytoin-induced gingival overgrowth is an adverse drug reaction affecting few individuals, on phenytoin therapy for its antiepileptic effect. Analysis of genetic variation of CYP2C9*2 gene was done to identify the action of metabolic enzyme cytochrome P 450 on this drug. The main background of this publication is a quick review about one of the molecular techniques used to identify the single-nucleotide polymorphism (SNP) using polymerase chain reaction coupled with restriction fragment length polymorphism (PCR-RFLP).

Materials And Methods: Deoxyribonucleic acid (DNA) was extracted from 5 ml of venous blood withdrawn from the individual, who had gingival overgrowth following phenytoin therapy. DNA was isolated, using the phenol-chloroform method. Isolated DNA was used for SNP analysis of CYP2C9*2 presentation. The basic procedure used for SNP analysis in our case was PCR-RFLP.

Results: Genetic variation of CYP2C9*2 in our case was homomutant.

Conclusion: The etiology of phenytoin-induced gingival overgrowth is always an enigma, but it is now becoming clearer that a multifactorial role may be involved in the cause. One of the factors analyzed was polymorphism of CYP2C9*2 gene and it was found to be homomutant in our case. Adverse drug reaction can be minimized, by either reducing the drug dosage or drug substitution. However, larger scale genome-wide study has to be carried out to confirm one of the etiopathogenesis as mutation of the CYP2C9 gene, in phenytoin-induced gingival overgrowth.