Enzyme changes in lichen planus.

Untreated cases of lichen planus have been studied by histochemical techniques. The acid phosphatase reaction in the transitional zone has been quantitatively estimated and compared with the adjacent relatively normal epidermis. It was found that despite a thickened and accentuated granular layer as seen by routine histological methods there was a marked reduction in the intensity of the acid phosphatase reaction. The glucose-6-phosphate dehydrogenase reaction was marked in the upper layers of the epidermis in active lesions of lichen planus. This is similar to psoriasis, but different from normal human epidermis. The suggestion by other authors that lichen planus is an inborn error of metabolism is discussed. The dendritic cells of the epidermis as studied by the ATPase reaction are virtually absent in regions of active lichen planus and the possible significance of this is mentioned. The horny layer gives a dense reaction for phospholipids in lichen planus and this is similar to psoriatic keratin. The significance of this finding is considered.