Paraneoplastic Pemphigus with Underlying Retroperitoneal Inflammatory Myofibroblastic Tumor: A Case Report and Review of the Literature.

Inflammatory myofibroblastic tumor (IMT) is a peculiar low-grade neoplasm of spindle cell fibroblasts and myofibroblasts in an inflammatory background. The lung is the most common site of involvement. Here, we report a case of paraneoplastic pemphigus (PNP)-associated with an extensive retroperitoneal IMT. The patient had a favourable response following treatment with a low dose of systemic steroid, mycophenolate mofetil, and intravenous immunoglobulin (IVIG). He subsequently underwent surgery for resection of the tumor with nephrectomy and five courses of IVIG were administered after surgery due to a minor relapse. He was in remission in her last follow-up visit 16 months after surgery. The occurrence of PNP with IMT is notable; early detection and treatment are crucial for this tumor-associated autoimmune disease.