APMLE Dermatology and Nail Disorders 1 — Questions and Answers
Question 1: Which dermatophyte species is most commonly responsible for tinea pedis (athlete's foot)?
- Candida albicans
- Trichophyton rubrum (Correct answer)
- Microsporum canis
- Epidermophyton floccosum
Correct answer: Trichophyton rubrum
Trichophyton rubrum is the most prevalent dermatophyte causing tinea pedis, accounting for approximately 70% of cases.
Question 2: A patient presents with a thickened, yellowed, and brittle toenail that separates from the nail bed. Which condition is most likely?
- Onychomycosis (Correct answer)
- Psoriatic onychodystrophy
- Onychogryphosis
- Paronychia
Correct answer: Onychomycosis
Onychomycosis presents with subungual hyperkeratosis, onycholysis, yellow/brown discoloration, and nail brittleness due to fungal invasion.
Question 3: What is the first-line systemic antifungal treatment for onychomycosis of the toenails?
- Fluconazole 150 mg weekly for 12 weeks
- Terbinafine 250 mg daily for 12 weeks (Correct answer)
- Itraconazole 200 mg daily for 6 weeks
- Griseofulvin 500 mg daily for 6 months
Correct answer: Terbinafine 250 mg daily for 12 weeks
Terbinafine 250 mg daily for 12 weeks is the preferred systemic treatment for toenail onychomycosis due to superior mycological cure rates.
Question 4: A patient with psoriasis presents with nail pitting, oil-drop discoloration, and onycholysis. Which nail finding is considered pathognomonic for psoriatic nail disease?
- Onycholysis
- Subungual hyperkeratosis
- Beau's lines
- Nail pitting (Correct answer)
Correct answer: Nail pitting
Nail pitting (small ice-pick depressions on the dorsal nail plate) is considered pathognomonic for psoriasis among the common nail changes.
Question 5: Which of the following describes onychogryphosis?
- Inward lateral curvature of the nail plate
- Extreme hypertrophy and curvature of the nail resembling a ram's horn (Correct answer)
- Separation of the nail plate from the nail bed
- Inflammation of the periungual tissue
Correct answer: Extreme hypertrophy and curvature of the nail resembling a ram's horn
Onychogryphosis (ram's horn nail) is characterized by extreme thickening and curved deformity of the nail plate, most often affecting the hallux in elderly patients.
Question 6: A plantar verruca (plantar wart) is caused by which pathogen?
- Molluscum contagiosum virus
- Herpes simplex virus type 1
- Human papillomavirus (HPV) (Correct answer)
- Staphylococcus aureus
Correct answer: Human papillomavirus (HPV)
Plantar warts are caused by Human papillomavirus (HPV), most commonly subtypes 1, 2, and 4, which infect the epidermis through microabrasions.
Question 7: When treating an ingrown toenail (onychocryptosis) with partial nail avulsion, which procedure permanently destroys the lateral nail matrix to prevent recurrence?
- Wedge resection
- Chemical matrixectomy with phenol (Correct answer)
- Zadik procedure
- Winograd procedure
Correct answer: Chemical matrixectomy with phenol
Chemical matrixectomy using 88% phenol applied to the exposed matrix after partial nail avulsion permanently ablates nail matrix cells, preventing nail regrowth in that segment.
APMLE Dermatology and Nail Disorders 1
Which dermatophyte species is most commonly responsible for tinea pedis (athlete's foot)?