Nail Psoriasis Treatment — SCE Dermatology MCQ

Correct answer: A — The nail plate acts as a physical barrier to drug penetration, limiting the amount of topical medication reaching the nail bed and matrix

Option A, the nail plate acts as a physical barrier to drug penetration, limiting the amount of topical medication reaching the nail bed and matrix, is correct. Nail psoriasis is notoriously difficult to treat topically because the densely packed keratin of the nail plate impedes diffusion of calcipotriol, corticosteroids and other agents down to the nail matrix and bed, where the pathological changes actually originate. This is why clinicians apply solutions under the free edge or via the proximal nail fold and hyponychium, and why adjuncts such as urea-based chemical avulsion, nail lacquers or iontophoresis are used to improve delivery. In more severe or matrix-predominant disease this barrier effect often necessitates intralesional corticosteroid injection or systemic and biologic therapy rather than reliance on topical treatment alone.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/skin-conditions