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Psoriatic Nail Disease — SCE Dermatology MCQ

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HardNail DisordersPsoriatic Nail DiseaseSCE Dermatology

A 60-year-old woman has nail psoriasis with oil drop (salmon patch) discolouration. This sign is specific to psoriasis. What is the histological correlate of the oil drop sign?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Focal parakeratosis and serous exudate of the nail bed

The best answer is “Focal parakeratosis and serous exudate of the nail bed”. NICE recommends treatment matched to severity, high-impact sites, functional burden, comorbidity and prior response; narrowband UVB is a finite specialist option for plaque or guttate psoriasis that topical therapy cannot control. The alternatives “Nail bed melanoma, after specialist assessment, when the full phenotype supports it”, “Melanin deposition, when the full phenotype supports it”, “Fungal invasion of the nail bed, within an appropriate UK pathway”, “Subungual haematoma, after clinicopathological correlation, after specialist assessment” are clinically adjacent possibilities, but they do not fit the defining morphology, distribution, histopathology, risk signal or management sequence in this stem.

Reference: NICE CG153 psoriasis recommendations: https://www.nice.org.uk/guidance/cg153/chapter/Recommendations