Increased numbers of mast cells in pemphigus vulgaris skin lesions. A histochemical study.

We have used a histochemical technique to study mast cells (MC) in skin biopsies of 8 patients suffering from pemphigus vulgaris (PV) and from 4 control volunteers. The MC were stained for 30 min with 0.5% toluidine blue, pH 0.5, counted and then restained for 5 days under the same conditions. This staining method allows the identification of two groups of MC, one that stains promptly (30 min) and one that stains after longer incubation times (5 days). After 30 min of staining, a slight increase was found in the number of MC in PV sections, in comparison with normal controls. However, when the 30 min stained sections were reincubated under the same conditions for 5 days, a significant increase in the number of MC in PV was found in comparison with 5-day-stained normal skin sections (p less than 0.005) and in comparison with 30-min-stained PV sections (p less than 0.005). The MC were distributed throughout the dermis and were concentrated in the upper dermis near hair follicles and vessels. The possible importance of the increased numbers of MC in PV is discussed.