Antidesmoplakin antibodies in pemphigus vulgaris

BACKGROUND: Besides being present in paraneoplastic pemphigus (PNP), circulating antidesmoplakin (DP) antibodies have been found anecdotally in other bullous diseases, including pemphigus foliaceus and pemphigus vulgaris. OBJECTIVES: To verify how frequent anti-DP antibodies are in pemphigus vulgaris. METHODS: We studied 48 sera from patients with proven pemphigus vulgaris (29 mucosal dominant pemphigus and 19 mucocutaneous pemphigus) by indirect immunofluorescence (IIF) with rat bladder epithelium (RBE) as a substrate and by immunoblotting (IB) on human keratinocyte cultures enriched in DP. RESULTS: Ten sera (21%) were positive in IIF on RBE. By IB, eight sera proved to have antibodies to both DP I (250 kDa) and DP II (210 kDa), one serum had antibodies directed to DP I only, and two sera to DP II only. CONCLUSIONS: Our data confirm that RBE is not a specific IIF substrate for the serological diagnosis of PNP. It remains a sensitive and specific substrate for the detection of anti-DP antibodies, which, in patients with pemphigus vulgaris, are probably caused by an epitope-spreading phenomenon