Definition Gingival hyperplasia is defined as an enlargement of the gingiva that is noninflammatory, produced by factors other than local irritation, and the result of an increased number of cells.1 Because gingival hyperplasia denotes a specific histologic diagnosis, clinicians must rule out other causes of gingival enlargement with biopsies of affected tissues.2 A common example is gingival enlargement caused by local irritation or inflammation.
Signalment Species. Seen more often in dogs than cats.
Breed predilection. Great Danes, collies, dalmatians, and Doberman pinschers; boxers appear to be overrepresented.3
- Breed predisposition
Pathophysiology Drug-induced gingival hyperplasia appears to be associated with alteration of calcium influx in gingival tissue. The exact mechanism of action has yet to be determined.4 Calcium antagonism may play a role in aldosterone synthesis by increasing testosterone levels.5 Studies have shown an increase in gingival hyperplasia associated with testosterone injections and a decrease in hyperplasia in castrated dogs receiving oxodipine.6 In patients receiving cyclosporine, transglutaminase levels are decreased in gingival tissue when calcium is not readily available, thereby decreasing apoptosis7 (Figure 1). In feline studies, cells resembling fibroblasts were stimulated to proliferate with the administration of phenytoin; this process resulted in gingival enlargement.8