Cat-scratch disease masquerading as post-transplant lymphoproliferative disorder.

Lymphadenopathy in an immunosuppressed patient raises the quintessential diagnostic dilemma: infection or malignancy? We present the case of a transplant recipient on anti-rejection prophylaxis admitted with acute fever, malaise and a swollen right axillary node. The patient had pancytopenia and tested positive for Epstein-Barr virus; nodal core biopsy demonstrated atypical plasma cell infiltration, immediately raising suspicion for post-transplant lymphoproliferative disorder. However, excisional biopsy and Bartonella henselae serology clarified a final diagnosis of cat-scratch disease-a potentially fatal zoonosis requiring a disparate treatment regimen. Here, we explore this patient's investigations, hospital course and recovery, with an emphasis on recognizing and differentiating these diagnostic mimics in post-transplant practice.