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New Lesions on Biologics — SCE Dermatology MCQ

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ModerateInflammatory DermatosesNew Lesions on BiologicsSCE Dermatology

A 40-year-old woman has psoriasis controlled on a biologic. She develops a new erythematous nodule on her arm. Before attributing it to psoriasis, her dermatologist considers other diagnoses. What is the most important reason to maintain a broad differential in patients on biologics?

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Correct answer: A — Immunosuppression from biologics increases infection risk — nodules/plaques may represent opportunistic infection (atypical mycobacteria, deep fungal), malignancy (NMSC, lymphoma), or other conditions that mimic psoriasis; biopsy threshold should be LOW

Patients on biologic immunosuppression require a heightened index of suspicion for non-psoriatic diagnoses: (1) infections — atypical mycobacteria, deep fungal infections, and reactivation of latent infections may present as skin nodules/plaques mimicking psoriasis; (2) malignancy — NMSC (SCC, BCC), lymphoma, and Merkel cell carcinoma; (3) drug-induced lesions — paradoxical psoriasis, injection site reactions; (4) unrelated new dermatoses. The biopsy threshold should be LOW for any new or atypical lesion in immunosuppressed patients. A non-healing nodule on a biologic should be biopsied and cultured (bacterial, mycobacterial, fungal) before assuming it is a psoriasis lesion.

Reference: BAD 2020 Biologic Safety