Derm Cases · Dermatology / General Medicine / Clinical Pharmacology
OSCE — assessment of photosensitivity with PLE versus drug-induced phototoxicity
An 8-minute OSCE station differentiating idiopathic photodermatoses (especially polymorphic light eruption) from drug-induced photosensitivity and photoaggravated disease, with photoprotection counselling, drug review, and escalation to phototesting/photopatch when indicated.
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Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station differentiating idiopathic photodermatoses (especially polymorphic light eruption) from drug-induced photosensitivity and photoaggravated disease, with photoprotection counselling, drug review, and escalation to phototesting/photopatch when indicated.
Brief (to candidate)
A 35-year-old woman develops itchy erythematous papules and plaques on the V of the neck, forearms and face within hours of sun exposure each spring; covered skin is spared. She recently started a thiazide diuretic. You have 8 minutes to differentiate polymorphic light eruption from drug phototoxicity/photoallergy, review culprits, and plan photoprotection and further tests.
[3]Candidate instructions
- Define photosensitivity and map lesions to UV-exposed sites (with classic spare zones).
- Differentiate PLE, drug-induced phototoxicity/photoallergy, solar urticaria, and chronic actinic dermatitis.
- Take a structured drug and chemical history (including plant/psoralen exposure).
- Outline photoprotection by phototype and disease.
- State when to refer for phototesting / photopatch testing.
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Pattern recognition | Eruption on photo-exposed skin (face, V-neck, dorsum hands/forearms); often spares under chin, upper eyelids, deep wrinkles; seasonal spring/summer flares suggest idiopathic photodermatosis such as PLE[3] |
| PLE features | Delayed (hours) itchy polymorphic papules/vesicles after sun; hardens with progressive summer exposure in some; diagnosis usually clinical; phototesting if atypical |
| Drug photosensitivity | Reviews phototoxic (exaggerated sunburn — tetracyclines, thiazides, amiodarone, NSAIDs, voriconazole, etc.) vs photoallergic (eczematous, delayed hypersensitivity) patterns; stop or substitute culprit when feasible[11] |
| Other key differentials | Solar urticaria (minutes, wheals); CAD (chronic eczematous photo-distributed, older patients, severe); lupus (ANA, systemic features); pellagra/porphyria if indicated; phytophotodermatitis (linear plant plant juice + UVA)[7] |
| Photoprotection | Broad-spectrum UVA+UVB sunscreen, adequate SPF and amount, clothing/hat, shade, peak-hour avoidance; phototype-tailored advice; visible-light considerations in deep pigmentary disorders if relevant[2] |
| Investigations | Drug chart review first; ANA/porphyrins when systemic/photodistributed scarring or blistering atypical; phototesting and photopatch for refractory/unclear photoallergy (e.g. sunscreen chemicals) |
| Management & communication | Mild PLE: photoprotection ± topical steroid for flares; prophylactic phototherapy/'hardening' in selected recurrent severe PLE; clear written drug advice |
Model key actions
- Localise to photo-exposed distribution; prefer PLE clinically for seasonal papular eruption, but actively exclude drug phototoxicity from thiazide.[3][11]
- Optimise UVA+UVB photoprotection and review/stop culprit drugs.[2]
- Escalate to phototesting/photopatch or consider CAD/connective tissue disease if chronic, severe, or atypical.[7]
Common errors
- Treating as simple sunburn without drug review.
- Missing photo-distribution clues (chin/eyelid sparing).
- Confusing solar urticaria timing (minutes) with PLE (hours).
- Recommending UVB-only thinking — many culprits and diseases need strong UVA protection.
- Failing to refer chronic severe photo-distributed eczema for CAD work-up.
References4ShowHide
- [2]Passeron T, Lim HW, Goh CL, et al. Photoprotection according to skin phototype and dermatoses: practical recommendations from an expert panel. Journal of the European Academy of Dermatology and Venereology : JEADV, 2021.PMID 33764577
- [3]Kadurina M, Kazandjieva J, Bocheva G. Immunopathogenesis and management of polymorphic light eruption. Dermatologic Therapy, 2021.PMID 34676645
- [7]Paek SY, Lim HW. Chronic actinic dermatitis. Dermatologic Clinics, 2014.PMID 24891057
- [11]Blakely KM, Drucker AM, Rosen CF. Drug-Induced Photosensitivity-An Update: Culprit Drugs, Prevention and Management. Drug Safety, 2019.PMID 30888626