Recurrent Cutaneous Plasmacytoma: Atypical Presentation of Post-transplant Lymphoproliferative Disorder

Introduction: Post Transplant Lymphoproliferative Disorder (PTLD) usually affects the allograft, GI tract or CNS. Plasmacytic PTLD is an unusual variant notable for lack of CD20 expression with limited reports in the literature. We present a complex case of cutaneous plasmacytic PTLD. Case Description: A 70-year-old lady s/p DDKT for IgAN in 2008 and a 2nd transplant for failing allograft in 2018 presented with multiple skin lesions on her right lower extremity (RLE). There was clinical concern for SCC but a biopsy surprisingly showed plasmacytic PTLD instead.Immunosuppression(IS) reduction & radiotherapy (RT) led to successful treatment. She unfortunately developed new lesions within 3 months of completing RT. An 8-week course of s/c daratumumab infusion was given after which her lesions appeared stable on PET-CT with low-level FDG uptake. Within 6 months, she developed multiple new skin lesions that remained consistent with plasmacytic PTLD. She was then treated with bortezomib but did not tolerate it due to significant GI side effects & weight loss. PET-CT showed more new nodular densities with increased uptake suspicious for recurrent PTLD. She was then transitioned to dara-CyBorD with resolution of all lesions except one small nodule on the RLE after 4 cycles that was surgically excised. A second new lesion appeared approximately one year after discontinuing dara-CyBorD but began to recede on its own. The patient completed 4 doses of rituximab and has had no new lesions as of her last follow-up. Discussion: Isolated cutaneous PTLD is very rare. Prior cases of plasmacytic PTLD describe responses with a combination of IS reduction & RT. Those with more advanced or relapsed disease have received myeloma-based therapies with varying levels of success. Given the absence of a standard of care for plasmacytic PTLD and our patient’s localized disease, we opted to gradually escalate treatment intensity over 4 years as the lesions recurred. To our knowledge, this is the first case report demonstrating successful use of dara-CyBorD in a KTR with cutaneous-limited PTLD.