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Erythroderma Differential — SCE Dermatology MCQ

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HardInflammatory DermatosesErythroderma DifferentialSCE Dermatology

A 55-year-old man develops erythroderma while on a biologic for psoriasis. His dermatologist suspects this may represent secondary loss of response with disease flare. What is the critical initial assessment?

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Correct answer: B — Exclude other causes of erythroderma (infection/sepsis, drug reaction, CTCL) before attributing to psoriasis flare — erythroderma in a patient on immunosuppression requires broad differential consideration

Erythroderma in a patient on biologic therapy requires careful differential diagnosis — not all erythroderma in psoriasis patients represents psoriasis flare. The differential includes: secondary infection/sepsis (immunosuppressed patients are at risk), drug reaction (to the biologic or concurrent medication), CTCL (which can mimic psoriatic erythroderma), and true psoriasis flare from biologic failure. Assessment should include: infection screen (blood cultures, CXR), drug history review, skin biopsy (to distinguish psoriasis from CTCL or drug reaction), and blood film/flow cytometry (to exclude Sézary syndrome). Only after excluding other causes should the erythroderma be attributed to psoriasis disease activity and treatment adjusted accordingly.

Reference: BAD 2020 Psoriasis/Biologic Guidelines