Intralesional Nail Injection — SCE Dermatology MCQ

Correct answer: E — Triamcinolone acetonide 2.5-5 mg/mL

The correct answer is E, triamcinolone acetonide 2.5-5 mg/mL. This is the corticosteroid preparation of choice for intralesional injection in nail psoriasis, whether the target is the nail matrix (pitting, ridging) or the nail bed (onycholysis, subungual hyperkeratosis, as in this patient). Low-concentration triamcinolone acetonide has a strong evidence base as the standard intralesional agent because it produces a durable local anti-inflammatory effect while allowing dose titration to minimise atrophy and depigmentation. Expert consensus and comparative trials confirm that 2.5-5 mg/mL achieves good clinical response with a lower rate of adverse effects (cuticle retraction, periungual atrophy) than higher concentrations, making it the practical first-line choice when topical therapy has failed and systemic treatment is not yet warranted. Why the other options are wrong: C. Betamethasone valerate: this is formulated for topical or intramuscular/intra-articular use, not as a standard intralesional nail preparation, and lacks the established dosing evidence base for nail injection. D. Clobetasol propionate: a very high potency topical steroid used on skin, not licensed or conventionally prepared for intralesional nail injection. A. Methylprednisolone: primarily used for intra-articular, intramuscular or systemic (e.g. pulsed) therapy; it is not the standard agent chosen for nail matrix or nail bed injection. B. Hydrocortisone: too low potency and too short acting to achieve meaningful, sustained suppression of inflammation within the nail apparatus. Key point: For nail psoriasis unresponsive to topical treatment, intralesional triamcinolone acetonide 2.5-5 mg/mL into the nail matrix or nail bed is the standard bridging therapy before escalation to systemic treatment.

Reference: Clinical and Experimental Dermatology (British Association of Dermatologists journal): 'A pilot study of intralesional methotrexate injections versus triamcinolone acetonide in patients affected by nail matrix psoriasis', 2022, https://pmc.ncbi.nlm.nih.gov/articles/PMC9303444/