IMG_4262.jpg
What is most likely diagnosis
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Based on the image analysis and textbook findings, I can now provide a thorough answer.
Most Likely Diagnosis: Mal Perforans (Neuropathic Plantar Ulcer)
The image shows a lesion on the plantar (sole) aspect of the foot with the following classic features:
| Feature | What is seen |
|---|---|
| Location | Plantar/plantar-lateral surface of the heel - a pressure point |
| Central ulcer/crater | Present - punched-out, deep central depression |
| Hyperkeratotic rim | Thick, yellowish, calloused ring surrounding the ulcer |
| White/cream exudate | Slough or macerated tissue at the base |
| Surrounding erythema | Pink-red halo indicating inflammation |
This triad of central ulceration + surrounding callus + pressure-point location on the sole is the hallmark of mal perforans (also called a neuropathic ulcer or diabetic foot ulcer).
Why Mal Perforans?
The Dermatology textbook (5th ed) specifically describes: "Neuropathic ulcerations at pressure points on the plantar surface... in a patient with diabetic neuropathy. Note the thick rim of callus." - this is an exact visual match.
The mechanism is:
- Peripheral neuropathy (usually diabetic) eliminates protective pain sensation
- Repetitive pressure/trauma at weight-bearing points goes unfelt
- A preulcerative callus builds up over the pressure site
- The callus eventually breaks down centrally, forming the characteristic punched-out crater
Differential Diagnoses to Consider
-
Plantar wart (Verruca plantaris) - also has a hyperkeratotic ring on the sole, but:
- Usually has thrombosed capillaries (black dots) visible on paring
- Typically painful on lateral compression
- No true ulcer base - paring reveals bleeding points, not a cavity
- Common in younger, otherwise healthy patients
-
Pressure ulcer / decubitus ulcer - possible if the patient is immobile, but location on a weight-bearing foot sole favors neuropathic origin
-
Ischemic ulcer - tends to have a pale/necrotic base, located on toes or lateral foot, and is very painful (unlike neuropathic ulcers)
Key Clinical Questions to Ask
- Does the patient have diabetes mellitus?
- Is there reduced or absent sensation on the foot?
- Any history of peripheral vascular disease?
- How long has the lesion been present, and is it painless? (painlessness strongly supports neuropathic etiology)
Recommended Next Steps
- Blood glucose / HbA1c
- Neurological exam (monofilament test, vibration)
- Vascular assessment (ankle-brachial index)
- Wound swab if infection is suspected
- Referral to podiatry/diabetic foot clinic
- Offloading (total contact cast or offloading footwear)
Note: This requires in-person clinical evaluation. The presence of surrounding erythema raises concern for early cellulitis or osteomyelitis, which would need urgent assessment. - Dermatology 2-Volume Set 5e; Rosen's Emergency Medicine
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