Increased Mucocutaneous FDG Activity in Paraneoplastic Pemphigus Associated With Follicular Dendritic Cell Sarcoma Transformed From Castleman Disease

Paraneoplastic pemphigus is a rare and fatal autoimmune mucocutaneous blistering disease associated with underlying tumors. We describe FDG PET/CT findings in a case of paraneoplastic pemphigus associated with pelvic follicular dendritic cell sarcoma transformed from Castleman disease. FDG PET/CT showed intense activity in the oral cavity, diffuse, heterogeneous activity in the skin, linear activity in the upper esophagus, focal activity in the anus, and heterogeneous activity in the pelvic tumor. This case indicates that paraneoplastic pemphigus should be considered as a differential diagnosis in patients with hypermetabolic mucocutaneous lesions.