Topical corticosteroids — SAQ

Stem

A 28-year-old woman presents with a 6-week history of itchy, erythematous, scaly patches on the flexural aspects of both elbows and knees. She has been applying a potent topical corticosteroid cream she obtained from a pharmacy, but the rash has worsened and is now more widespread. She has a history of childhood eczema and seasonal allergic rhinitis. On examination, there are well-demarcated erythematous plaques with silvery scale on the extensor elbows and knees, and smaller eczematous patches in the antecubital fossae. She asks whether she should continue using the steroid cream.

Questions

a) Classify topical corticosteroids by potency and give one example for each tier. (2 marks)

^[4][6]b) What are the likely diagnoses for the elbow/knee plaques and the flexural patches? How would you distinguish between them? (2 marks)

c) Outline the principles of safe topical corticosteroid prescribing, including potency selection, vehicle, and the fingertip unit. (3 marks)

^[4][5]d) What are the local and systemic adverse effects of topical corticosteroids, and how can they be minimized? (3 marks)

^[4]

Model answer

a) Topical corticosteroids are classified into four potency tiers: mild (hydrocortisone 0.5–2.5%); moderate (clobetasone butyrate 0.05%, betamethasone valerate 0.025%); potent (mometasone furoate 0.1%, betamethasone valerate 0.1%); and very potent (clobetasol propionate 0.05%).^[4]

^[3]b) The extensor plaques with silvery scale are most consistent with plaque psoriasis; the flexural eczematous patches are most consistent with atopic dermatitis of the flexures. Distinguishing features include the well-demarcated, thick, silvery-scaled plaques on extensor surfaces in psoriasis, versus ill-defined, pruritic, eczematous patches in flexural atopic dermatitis. Auspitz sign and Koebner phenomenon support psoriasis; a history of atopy and flexural involvement support atopic dermatitis. If scale is present, a KOH preparation should be performed to exclude tinea before using potent steroids.

^[2]c) The principles are: (1) choose the weakest effective potency for the shortest necessary duration; (2) match potency to body site — face/eyelids/flexures should receive only mild TCS, while palms/soles and thick plaques may need potent/very potent agents; (3) match the vehicle to the lesion — ointment for dry, scaly plaques; cream for wet, acute eczema; lotion/foam/gel for hair-bearing areas; (4) use the fingertip unit to standardise quantity — 1 FTU ≈ 0.5 g and covers two adult palms (about 2% BSA); (5) set a stop/review date, usually 1–2 weeks for mild-moderate disease and 2–4 weeks for thick plaques; (6) taper by reducing frequency or potency to avoid rebound; and (7) co-prescribe emollients and, where appropriate, steroid-sparing agents.

^[1]d) Local adverse effects include skin atrophy, striae, telangiectasia, purpura, acneiform eruptions, periorificial dermatitis, hypopigmentation, hypertrichosis, delayed wound healing, and tinea incognito if used on an undiagnosed fungal infection. Systemic adverse effects include HPA axis suppression, iatrogenic Cushing's syndrome, growth retardation in children, hyperglycaemia, osteoporosis, and cataract/glaucoma with periorbital use. They are minimised by using the lowest effective potency, limiting duration, avoiding high-absorption sites, using the FTU, applying emollients, and introducing steroid-sparing agents (tacrolimus, pimecrolimus, calcipotriene) for maintenance.

References6ShowHide

1. [1]Chu DK, Chu AWL, Rayner DG, et al. Topical treatments for atopic dermatitis (eczema): Systematic review and network meta-analysis of randomized trials J Allergy Clin Immunol, 2023.PMID 37678572
2. [2]Frazier W, Bhardwaj N. Atopic Dermatitis: Diagnosis and Treatment Am Fam Physician, 2020.PMID 32412211
3. [3]Allenby CF, Main RA, Marsden RA, Sparkes CG. Effect on adrenal function of topically applied clobetasol propionate (Dermovate) Br Med J, 1975.PMID 1203701
4. [4]Stacey SK, McEleney M. Topical Corticosteroids: Choice and Application Am Fam Physician, 2021.PMID 33719380
5. [5]Stacey SK, McEleney M. Topical Corticosteroids: Choice and Application Am Fam Physician, 2021.PMID 33719380
6. [6]Stacey SK, McEleney M. Topical Corticosteroids: Choice and Application Am Fam Physician, 2021.PMID 33719380