Derm Cases · Dermatology / Infectious Disease / Primary Care
OSCE — groin, feet and nails: tinea cruris, pedis and onychomycosis
An 8-minute OSCE station on recognition of dermatophyte infection of groin, feet and nails, KOH/culture confirmation, distinction from candidal intertrigo, oral terbinafine dosing for onychomycosis, and red flags including diabetic foot risk and terbinafine-resistant T. indotineae.
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Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on recognition of dermatophyte infection of groin, feet and nails, KOH/culture confirmation, distinction from candidal intertrigo, oral terbinafine dosing for onychomycosis, and red flags including diabetic foot risk and terbinafine-resistant T. indotineae.
Brief (to candidate)
A 42-year-old man has a pruritic annular groin rash for 3 months, macerated interdigital toe webs, and thickened yellowish toenails. He walks barefoot in a gym locker room and has well-controlled type 2 diabetes. You have 8 minutes to diagnose the three related infections, confirm mycology, and plan topical vs systemic therapy with safety-netting.
Candidate instructions
- Examine groin, feet and nails as a linked dermatophyte reservoir.
- Differentiate tinea cruris from candidal intertrigo and inverse psoriasis.
- Plan KOH / culture / PAS nail confirmation before long systemic courses.
- Prescribe correct topical and oral terbinafine regimens.
- Address recurrence prevention, diabetic foot risk, and resistant dermatophytes.
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Recognition | Tinea cruris: annular active border in groin, typically spares scrotum; tinea pedis interdigital/moccasin/vesicular patterns; onychomycosis with onycholysis, subungual debris, dystrophy[1][15] |
| Linked exam | Always inspect feet and nails when groin disease presents (autoinoculation / two-feet–one-hand patterns)[1] |
| Differential | Candidal intertrigo involves scrotum/penis with satellite pustules; inverse psoriasis; erythrasma (Wood lamp coral-red); contact dermatitis |
| Investigations | Skin scraping KOH; nail clippings ± PAS (most sensitive single nail test); culture when refractory or resistance suspected[2][7] |
| Topical Rx | Allylamine/azole cream for pedis/cruris (e.g. terbinafine 1% daily for 1–4 weeks); dry interdigital spaces; treat concurrent foot disease to protect the groin[1][15] |
| Systemic nails | Oral terbinafine 250 mg daily: 6 weeks fingernails, 12 weeks toenails; check LFTs/drug interactions as per local protocol; itraconazole alternative with CYP/heart-failure cautions[2][7] |
| Red flags | Ulcerative interdigital disease in diabetes/vascular disease → cellulitis risk; extensive refractory disease from endemic areas → consider T. indotineae (terbinafine resistance)[16] |
Model key actions
- Link cruris + pedis + unguium as one dermatophyte continuum and examine all three sites.[1]
- Confirm diagnosis before prolonged oral therapy; treat nails with terbinafine 250 mg daily for 12 weeks for toenails.[2][7]
- Prevent recurrence (foot hygiene, treat family fomites, keep groin dry) and escalate if resistant / diabetic foot risk.[15][16]
Common errors
- Treating only the groin while ignoring the foot/nail reservoir.
- Diagnosing candidiasis because the scrotum is involved without re-examining morphology.
- Long oral antifungals without mycological confirmation.
- Under-dosing toenail courses (stopping at 2–4 weeks).
- Missing cellulitis risk in diabetic interdigital tinea.
References5ShowHide
- [1]Leung AK, Barankin B, Lam JM, et al. Tinea pedis: an updated review. Drugs in Context, 2023.PMID 37415917
- [2]Lipner SR, Scher RK. Onychomycosis: Treatment and prevention of recurrence. Journal of the American Academy of Dermatology, 2019.PMID 29959962
- [7]Frazier WT, Santiago-Delgado ZM, Stupka KC 2nd. Onychomycosis: Rapid Evidence Review. American Family Physician, 2021.PMID 34652111
- [15]Ely JW, Rosenfeld S, Seabury Stone M. Diagnosis and management of tinea infections. American Family Physician, 2014.PMID 25403034
- [16]Sonego B, Corio A, Mazzoletti V, et al. Trichophyton indotineae, an Emerging Drug-Resistant Dermatophyte: A Review of the Treatment Options. Journal of Clinical Medicine, 2024.PMID 38930086