A patient taking phenytoin for epilepsy develops gingival hyperplasia. The mechanism underlying this adverse effect involves:

• A Inhibition of sodium channels in gingival keratinocytes causing hyperproliferation
• B Direct immunoglobulin deposition in gingival connective tissue
• C Phenytoin-induced folate deficiency causing gingival stromal changes
• D Activation of fibroblast proliferation via TGF-beta1 upregulation ✓

Explanation

Phenytoin-induced gingival overgrowth results from phenytoin stimulating TGF-beta1 production in gingival fibroblasts, which drives collagen synthesis and fibroblast proliferation. This creates an accumulation of collagen-rich connective tissue rather than a true hyperplasia of all gingival cells. The effect is worsened by poor oral hygiene (bacterial plaque). Folic acid supplementation and meticulous oral hygiene can reduce but not fully prevent the overgrowth.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.