A case of paraneoplastic pemphigus associated with Castleman's disease presenting as erosive lichen planus.

Paraneoplastic pemphigus (PNP) is a debilitating chronic blistering mucocutaneous disease associated with an underlying neoplasm and a poor prognosis. We present a patient who had been diagnosed and treated for recalcitrant erosive mucocutaneous lichen planus for 3 years with little success. Further investigations established the diagnosis of PNP with underlying Castleman's disease. This case highlights the importance of repeated investigations to exclude PNP in patients with recalcitrant mucosal erosions, especially if atypical features are present.