Patterns of periodic acid–schiff staining in subepidermal bullous disorders with emphasis on bullous pemphigoid

Background: Direct immunofluorescence (DIF) including salt split skin technique is quintessential in the diagnosis of subepidermal bullous disorders. These techniques are expensive and require technical expertise, limiting their diagnostic utility. The property of periodic-acid–Schiff to stain the basement membrane and the patterns produced by it was observed in a cohort of subepidermal bullous disorders, to see if it offers an alternative cost-effective testing method. Materials and Methods: This was a retrospective, observational study conducted in the department of general pathology, in a tertiary care medical center, over a period of 4 years. Only those cases for which paraffin sections, DIF and direct salt split skin immunofluorescence technique were available were included. The levels of anti-bullous pemphigoid (BP) antibodies were collected where available. Results: Of the 21 cases analyzed, 15 were BP, two each of epidermolysis bullosa acquisita (EBA) and lichen planus pemphigoides (LPP), one each of porphyria cutanea tarda (PCT), and bullous systemic lupus erythematosus (SLE). All the cases of BP, LPP and EBA showed a floor pattern of staining with periodic acid–Schiff (PAS) stain. Roof pattern of staining was observed in bullous SLE and PCT. PAS was found to be useful in diagnosing BP, especially in conjunction with an eosinophil rich bulla and anti-BP antibodies. Conclusion: We found that PAS stain could be an adjunct to hematoxylin and eosin stain when the diagnosis of BP is in doubt. However, larger sample size is needed to study its utility in other subepidermal bullous disorders.