Successful Desensitization to Trimethoprim-Sulfamethoxazole for Pneumocystis Pneumonia in a Challenging Case of Second Kidney Transplantation: A Case Report and Literature Review.

Pneumocystis jirovecii pneumonia (PJP) is a life-threatening opportunistic infection that predominantly affects immunocompromised individuals, with trimethoprim-sulfamethoxazole (TMP-SMX) remaining the first-line therapy. However, hypersensitivity reactions to sulfonamides often hinder its administration, leading to a critical therapeutic dilemma. Crucially, desensitization is absolutely contraindicated in severe reactions such as Stevens-Johnson syndrome or toxic epidermal necrolysis, and should be reserved exclusively for patients with mild-to-moderate hypersensitivity. For these appropriately selected patients, drug desensitization presents a viable solution, robust evidence supporting its application in high-risk transplant recipients, especially in emergent infectious settings, is notably limited. This article reports the successful management of PJP in a second kidney transplant recipient through a tailored TMP-SMX oral desensitization protocol, demonstrating its safety and efficacy in this complex clinical scenario. Accompanied by a systematic literature review, we further synthesize and evaluate existing published desensitization strategies and discuss key practical considerations for protocol implementation and monitoring. Collectively, this detailed case report and integrated review aim to provide clinicians with a structured, evidence-based approach to implementing sulfonamide desensitization, which is particularly crucial for vulnerable patient populations with severely limited therapeutic alternatives.