DPM Dermatological Conditions of the Foot 3 — Questions and Answers
Question 1: A patient presents with painful grouped vesicles on one side of the foot following the dermatome. What is the diagnosis?
- Dyshidrotic eczema
- Herpes zoster (Correct answer)
- Impetigo
- Bullous pemphigoid
Correct answer: Herpes zoster
Herpes zoster presents with painful grouped vesicles in a dermatomal distribution caused by reactivation of varicella-zoster virus.
Question 2: Which finding distinguishes a soft corn (heloma molle) from a hard corn (heloma durum)?
- Location on the dorsum vs. sole
- Maceration from moisture between toes vs. dry appearance (Correct answer)
- Viral etiology vs. mechanical
- Presence of a central core vs. diffuse thickening
Correct answer: Maceration from moisture between toes vs. dry appearance
Soft corns occur in moist interdigital spaces and appear macerated and white, while hard corns on toe prominences remain dry.
Question 3: Erythrasma of the toe webs is caused by which organism?
- Candida albicans
- Corynebacterium minutissimum (Correct answer)
- Staphylococcus aureus
- Trichophyton mentagrophytes
Correct answer: Corynebacterium minutissimum
Erythrasma is a superficial bacterial infection caused by Corynebacterium minutissimum, which fluoresces coral-red under Wood's lamp.
Question 4: A patient has recurrent, intensely pruritic vesicles on the lateral aspects of the toes and the instep. No fungal elements are found on KOH prep. What is the most likely diagnosis?
- Moccasin-type tinea pedis
- Dyshidrotic eczema (pompholyx) (Correct answer)
- Allergic contact dermatitis
- Bullous impetigo
Correct answer: Dyshidrotic eczema (pompholyx)
Dyshidrotic eczema presents with deep-seated, pruritic vesicles on the lateral toes and instep with a negative KOH preparation.
Question 5: What is the most appropriate initial treatment for a Grade 1 pressure ulcer on the heel of a bedridden patient?
- Surgical debridement
- Offloading and moisture barrier cream (Correct answer)
- Systemic antibiotics
- Split-thickness skin graft
Correct answer: Offloading and moisture barrier cream
Grade 1 pressure ulcers show intact skin with non-blanchable erythema and are managed with pressure offloading and skin protection.
Question 6: Subungual melanoma of the hallux most commonly presents as:
- White discoloration of the entire nail plate
- Longitudinal melanonychia with Hutchinson's sign (Correct answer)
- Transverse ridging of the nail
- Yellow-green discoloration of the distal nail
Correct answer: Longitudinal melanonychia with Hutchinson's sign
Subungual melanoma typically presents as longitudinal melanonychia (dark streak) with pigment extension onto the proximal nail fold, known as Hutchinson's sign.
Question 7: A Wood's lamp examination of a foot lesion shows brilliant green fluorescence. Which condition does this indicate?
- Erythrasma
- Pseudomonas infection (Correct answer)
- Pityriasis versicolor
- Tinea pedis
Correct answer: Pseudomonas infection
Pseudomonas aeruginosa produces pyocyanin pigment, which fluoresces brilliant green under Wood's lamp examination.
DPM Dermatological Conditions of the Foot 3
A patient presents with painful grouped vesicles on one side of the foot following the dermatome.
What is the diagnosis?