Paraneoplastic pemphigus in primary peritoneal clear cell carcinoma: a multidisciplinary management approach.

Background: Paraneoplastic pemphigus (PNP) or paraneoplastic autoimmune multiorgan syndrome (PAMS) is a rare, mucocutaneous blistering condition associated with high morbidity and mortality. Most reported cases occur in the setting of lymphoproliferative malignancies, with limited data describing associations with solid tumors. Additionally, standardized diagnostic criteria and management guidelines remain lacking. We describe the first, to our knowledge, case of PNP/PAMS associated with primary peritoneal clear cell carcinoma. Case Presentation: A 47-year-old woman with recurrent, platinum-resistant primary peritoneal clear cell carcinoma presented with painful oral mucosal erosions, intermittent epistaxis, and a pruritic cutaneous eruption involving the trunk, groin, and lower extremities approximately four weeks after her fourth cycle of gemcitabine, cisplatin, and bevacizumab. Skin punch biopsy, serologies, and clinical findings were consistent with PNP/PAMS. She was treated with high-dose intravenous corticosteroids, followed by multiple adjunctive systemic and supportive therapies through a multidisciplinary approach; however, her recalcitrant and aggressive mucocutaneous disease progressed, contributing to significant clinical decline. She ultimately transitioned to comfort-focused care and died from complications of her underlying malignancy. Conclusion: This case highlights the diagnostic and therapeutic challenges of PNP/PAMS in patients with solid tumors and underscores the importance of multidisciplinary management in the absence of standardized treatment guidelines.