[Paraneoplastic pemphigus revealing dendritic cell sarcoma originating from Castleman's disease of the neck].

INTRODUCTION: Paraneoplastic pemphigus is associated with Castleman's disease. We report a case of paraneoplastic pemphigus at the stage of the sarcomatous transformation of Castleman's disease, present for many years but without concomitant paraneoplastic pemphigus. The pemphigus was manifested by the most unusual, exclusive, involvement of the mucosa of the mouth and lung.

OBSERVATION: A 32 year-old man suffering from extensive ulceration of the oral mucosa was hospitalized in December 2000 for alteration in his general status of health and acute respiratory failure. The search for intercellular anti-substance antibodies on rat spleen was positive, corresponding to anti-envoplakin IgG and leading to the diagnosis of paraneoplastic pemphigus. The thoracic x-ray and scan revealed a hilum tumor, the histological examination of which confirmed the diagnosis of Castleman's disease concomitant to sarcomatous transformation. Following surgical treatment, the respiratory failure worsened. The patient improved with systemic corticosteroids at the dose of 2 mg/kg/d and chemotherapy was initiated. The patient died suddenly within the context of acute respiratory failure, three months after surgery.

DISCUSSION: This is a case of paraneoplastic pemphigus of unusual clinical and biological expression: exclusively mucosal involvement with obliterating bronchiolitis, explained by the isolated presence of antibodies recognizing envoplakin, without anti-desmoglein. The transformation of the Castleman tumor into a sarcoma may have unmasked intra-cellular antigens (plakins), initiating the specific immune reaction.