Burned by Diplopia

His rash progressed with extensive perioral and skin desquamation involving 70% of the skin surface requiring transfer to a burn unit. The skin biopsy showed desquamation and lichenoid inflammation consistent with paraneoplastic pemphigus. Within a week, he succumbed to cardiopulmonary arrest. His constellation of symptoms is unified by a paraneoplastic process from follicular dendritic cell sarcoma (FDCS) causing: paraneoplastic pemphigus (PP), polymyositis, myasthenia gravis and autoimmune neutropenia. His serum paraneoplastic panel was positive for Acetylcholine Receptor Binding Antibody (36.8 nmol/L, ref <0.02), Acetylcholine Receptor Modulating Antibody (96% ref 0-20%) and Striational Antibody (1:2457 ref <1:60). Paraneoplastic pemphigus is a rare, life-threatening autoimmune bullous disease characterized by severe, intractable mucositis and polymorphous skin eruption, often times difficult to differentiate from Stevens-Johnson syndrome (SJS). Approximately 75% of SJS are caused by medications, 25% by infections and rarely malignancy (<1%). Our patient received filgastrim to treat neutropenia, and this drug was initially thought to be the cause of the extensive skin rash. Differentiating PP from SJS by skin biopsy is extremely important because PP is commonly associated with neoplasm while SJS is not. In addition, the use of IVIG is beneficial in PP and potentially harmful in SJS. In two thirds of cases, PP occurs in patients with a known neoplasm, while one third of patients develop the mucocutaneous disease before the neoplasm is detected. In one case report, PP was the first manifestation of FDCS (Kwein-lan et al). Castleman's disease (CD) represents a non-neoplastic lymphoproliferative disorder with various clinical and morphological features that have been associated with FCDS. Despite this known association between CD and FDCS, there have only been few reported cases of FDCS with pre-existing CD, especially in abdominal lesions.