Direct fluorescence on tzanck smears: A rapid test to confirm pemphigus

To the Editor

Acantholysis,a process by which epidermal cells loose their cohesiveness is the essential abnormality in the pemphigus group of disorders. Cytologic examination (Tzanck smear) of the intact bulla is one of the methods for the rapid demonstration of these acantholytic cells. However, it has some limitations because acantholytic cells are occasionally seen in various non acantholytic vesiculobullous diseases.[1]

The pemphigus antigen is present not only in the desmosome but also on the cell membrane of keratinocytes.[2] The pemphigus antibody which is an IgG immunoglobulin is present intercellularly in almost all cases of pemphigus.[3]

Direct immunofluorescence on full thickness skin biopsy is the classical method for demonstrating intercellular antibodies in the pemphigus group of disorders.[1]

This study was done on six consecutive patients with typical clinical and light microscopic features of pemphigus vulgaris. Tzanck smears were made from the floor of fresh bullae. Direct immunofluorescence using fluroscein isothiocyanate labelled anti IgG on the Tzanck smears demonstrated typical fluorescence on the cytoplasmic borders of the acantholytic cells [Figure - 1]. Where the cells were in clusters, the honey comb pattern of fluorescence typical of pemphigus was demonstrated.

This method, we feel can be used for rapid confirmation of the diagnosis of pemphigus in cases where acantholytic cells are demonstrated in Tzanck smear. A skin biopsy which is an expensive, time consuming and invasive procedure can thus be avoided.