SPEX Dermatology 5 — Questions and Answers
Question 1: A 45-year-old woman presents with target-like lesions on her palms and oral erosions after starting trimethoprim-sulfamethoxazole. What is the most likely diagnosis?
- Erythema multiforme major (Stevens-Johnson syndrome) (Correct answer)
- Fixed drug eruption
- Toxic epidermal necrolysis
- Pityriasis rosea
Correct answer: Erythema multiforme major (Stevens-Johnson syndrome)
Stevens-Johnson syndrome (erythema multiforme major) is characterized by target lesions, mucosal erosions, and is commonly triggered by sulfonamides.
Question 2: Which feature distinguishes a melanoma from a benign melanocytic nevus using the ABCDE criteria?
- Diameter less than 6 mm
- Symmetric shape
- Uniform tan color
- Border irregularity (Correct answer)
Correct answer: Border irregularity
Border irregularity (notched, scalloped, or ill-defined edges) is a key ABCDE criterion distinguishing melanoma from benign nevi.
Question 3: A newborn has vesicles grouped in a dermatomal pattern on the trunk. Tzanck smear shows multinucleated giant cells. What is the most appropriate treatment?
- Topical acyclovir cream
- Oral valacyclovir
- IV acyclovir (Correct answer)
- Observation only
Correct answer: IV acyclovir
Neonatal herpes simplex virus infection is a medical emergency requiring immediate IV acyclovir due to the risk of dissemination and mortality.
Question 4: A patient presents with comedones, inflammatory papules, and nodules on the face and back. Which topical agent works by normalizing follicular keratinization and is considered a first-line treatment for acne?
- Benzoyl peroxide
- Topical retinoids (tretinoin) (Correct answer)
- Topical clindamycin
- Azelaic acid
Correct answer: Topical retinoids (tretinoin)
Topical retinoids normalize follicular keratinization, prevent microcomedo formation, and are considered the backbone of topical acne therapy.
Question 5: Which HLA type is strongly associated with psoriasis and psoriatic arthritis?
- HLA-B27
- HLA-Cw6 (Correct answer)
- HLA-DR4
- HLA-B51
Correct answer: HLA-Cw6
HLA-Cw6 (now designated HLA-C*06:02) is the major genetic risk factor for psoriasis vulgaris and psoriatic arthritis.
Question 6: A 70-year-old farmer has a rough, scaly lesion on sun-damaged skin of his forehead. Biopsy reveals atypical keratinocytes confined to the epidermis. What is this lesion?
- Seborrheic keratosis
- Bowen's disease (SCC in situ)
- Actinic keratosis (Correct answer)
- Keratoacanthoma
Correct answer: Actinic keratosis
Actinic keratosis is a premalignant lesion on sun-damaged skin showing atypical keratinocytes in the lower epidermis without full-thickness involvement.
Question 7: Which medication used for acne treatment is absolutely contraindicated in pregnancy due to teratogenicity?
- Topical benzoyl peroxide
- Oral doxycycline
- Oral isotretinoin (Correct answer)
- Topical clindamycin
Correct answer: Oral isotretinoin
Oral isotretinoin is a Category X teratogen causing severe birth defects and requires enrollment in the iPLEDGE program for all patients.
SPEX Dermatology 5
A 45-year-old woman presents with target-like lesions on her palms and oral erosions after starting trimethoprim-sulfamethoxazole.
What is the most likely diagnosis?