The Enigma of Paradoxical Reactions to Biological Therapies.

The advent of targeted biological agents has revolutionized the treatment approach for immune-mediated inflammatory diseases (IMIDs) in rheumatology and dermatology. However, these agents can lead to paradoxical immune-mediated inflammatory reactions (PRs), presenting challenges in clinical management. This case series aims to demonstrate diverse PRs associated with biologic therapies in IMID patients, shedding light on their clinical manifestations and management strategies. Five cases of IMID patients receiving targeted biologic therapies who developed PRs were retrospectively analyzed. Clinical presentations, histopathological findings, and treatment outcomes were documented. The PRs observed included pityriasis rosea-like drug reactions, eczematous reactions, lichenoid drug eruptions, and fixed drug eruptions. Histopathological examination revealed characteristic patterns corresponding to each PR type. Management strategies involved discontinuation or switching of biologic agents, resulting in resolution of cutaneous manifestations. This case series underscores the importance of recognizing and managing PRs in IMID patients undergoing biologic therapy. Further research is warranted to elucidate underlying mechanisms and guide therapeutic decisions, particularly with the emergence of biosimilars and potential cross-reactivity concerns.