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What's this disease
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Reading File
Finding Sources
Finding Sources
Reading File
Reading File
Based on the clinical images and textbook evidence, here is my full analysis:
Clinical Findings
Both images show the plantar surfaces (soles) of both feet with:
- Bilateral, symmetrical involvement - affecting both feet equally
- Diffuse, thick hyperkeratosis - dense, rigid thickening of the skin, most severe at the heels and metatarsal heads
- Coarse lamellar (plate-like) scaling - chalky-white to grayish-white dry scales covering the entire sole
- Deep linear fissures - especially around the heel margins, which can be painful and may bleed
- "Moccasin" distribution - scaling covers the entire plantar surface and wraps around the lateral borders of the foot (like a moccasin shoe outline)
- Relative sparing of the dorsum (top of the foot)
Most Likely Diagnosis: Moccasin-Type Tinea Pedis (Fungal Foot Infection)
This is the classic presentation of chronic moccasin-type tinea pedis, caused most commonly by Trichophyton rubrum. As described in Dermatology 5th Edition, this type presents with:
"Diffuse hyperkeratosis, erythema, scaling and fissures on one or both plantar surfaces; frequently chronic."
The bilateral symmetrical distribution, diffuse plantar hyperkeratosis, and moccasin pattern strongly point to T. rubrum infection, which is notorious for causing chronic, therapy-resistant hyperkeratotic tinea pedis.
Differential Diagnoses to Consider
| Condition | Why it fits | Why it might not |
|---|---|---|
| Moccasin Tinea Pedis (top pick) | Bilateral moccasin pattern, thick scaling, chronic appearance | Needs KOH confirmation |
| Palmoplantar Keratoderma (PPK) | Diffuse plantar thickening with fissures | Usually hereditary, often starts in childhood, check palms |
| Plantar Psoriasis | Thick plaques, fissures, silvery scale | Usually shows erythema, nail pitting, or other psoriatic lesions elsewhere |
| Severe Xerosis / Cracked Heels | Dry skin, fissuring | Usually less severe and not moccasin-distributed |
| Chronic Eczema | Lichenification, dryness | Usually pruritic with history of atopy |
How to Confirm
- KOH (potassium hydroxide) preparation of skin scrapings - if hyphae are seen, fungal infection is confirmed
- Fungal culture for species identification
- Check the palms - moccasin tinea pedis is often associated with tinea manuum (one or both hands)
Treatment
For tinea pedis (moccasin type):
- Topical: Terbinafine 1% cream daily for 2-4 weeks (allylamines are superior to azoles for this type) - Textbook of Family Medicine 9e
- Oral (preferred for moccasin type, as topicals often fail to penetrate thick hyperkeratosis): Terbinafine 250 mg daily for 2-6 weeks or itraconazole 200 mg twice daily for 1 week (pulse therapy)
- Keratolytic adjunct: Urea 20-40% cream or salicylic acid cream to soften and reduce the thick scale before antifungal penetration
- Hygiene: Keep feet dry, change socks frequently, avoid occlusive footwear, use antifungal powder
Important: Moccasin-type tinea pedis is notoriously chronic and resistant to topical therapy alone. Oral antifungal treatment is usually required. The person in these photos should see a dermatologist or general practitioner, especially given the depth of the fissures, which are potential entry points for bacterial cellulitis.
Disclaimer: This is an educational assessment based on clinical photography. A definitive diagnosis requires in-person examination, skin scrapings (KOH prep), and possibly fungal culture.
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