Mast cells in oral erythema multiforme.

We compared the number of mast cells in erythema multiforme lesions, in clinically healthy mucosa between the EM attacks and in healthy mucosa from healthy volunteers. The mast cell count in patients with erythema multiforme was numerically higher than in healthy controls, but the differences were not statistically significant. In erythema multiforme lesions the mast cell count was low in the intensely inflamed superficial lamina propria, but high in normal appearing mucosa between the attacks suggesting local mast cell degranulation in the most intensely inflamed areas.