Ruptured bullae lead to the formation of erosions. Involvement of the oral mucosa gives rise to painful ulcers. This is done to confirm the diagnosis. In order to see the diagnostic features, new, rather than old lesion should be chosen for biopsy. Classically, one should find suprabasal blister with acantholysis in histology.
Perilesional skin shows the presence of intercellular IgG deposition within the epidermis.
The titre correlates with the disease activity and is a good parameter for monitoring the disease progress. A more than twofold increase in titre is an indication of relapse. This test is not casually available. It can only be done in a few hospital-based centres with special arrangement. A cytology method revealing the characteristic acantholytic cells.