SPEX Dermatology 4 — Questions and Answers
Question 1: A patient presents with a well-demarcated, erythematous plaque with silvery scale on the elbow. The Auspitz sign is positive. What is the most likely diagnosis?
- Psoriasis vulgaris (Correct answer)
- Seborrheic dermatitis
- Pityriasis rosea
- Tinea corporis
Correct answer: Psoriasis vulgaris
Psoriasis vulgaris classically presents with well-demarcated erythematous plaques with silvery scale and a positive Auspitz sign (pinpoint bleeding upon scale removal).
Question 2: Which dermatophyte is most commonly responsible for tinea capitis in the United States?
- Microsporum canis
- Trichophyton tonsurans (Correct answer)
- Epidermophyton floccosum
- Trichophyton rubrum
Correct answer: Trichophyton tonsurans
Trichophyton tonsurans is the most common cause of tinea capitis in the United States, typically not fluorescing under Wood's lamp.
Question 3: A 65-year-old man has a pearly, telangiectatic papule on his nose that has slowly enlarged over 2 years. Biopsy shows palisading nuclei at the periphery of tumor islands. What is the diagnosis?
- Squamous cell carcinoma
- Melanoma
- Basal cell carcinoma (Correct answer)
- Merkel cell carcinoma
Correct answer: Basal cell carcinoma
Basal cell carcinoma characteristically shows palisading of nuclei at the periphery of tumor nests on histology, with a pearly, telangiectatic clinical appearance.
Question 4: Which immunofluorescence pattern is characteristic of pemphigus vulgaris?
- Linear IgG at the dermal-epidermal junction
- Granular IgA at dermal papillae tips
- Intercellular IgG in a 'fishnet' pattern (Correct answer)
- C3 deposits at the basement membrane zone
Correct answer: Intercellular IgG in a 'fishnet' pattern
Pemphigus vulgaris shows intercellular IgG deposition in a 'fishnet' or 'chicken wire' pattern on direct immunofluorescence due to anti-desmoglein antibodies.
Question 5: A patient with HIV presents with violaceous papules on the hard palate and lower extremities. What is the causative organism?
- Bartonella henselae
- Human herpesvirus 8 (Correct answer)
- Epstein-Barr virus
- Cryptococcus neoformans
Correct answer: Human herpesvirus 8
Kaposi sarcoma, which presents with violaceous plaques and papules in immunocompromised patients, is caused by Human herpesvirus 8 (HHV-8).
Question 6: A 30-year-old woman has butterfly-shaped erythema across her cheeks and nose. ANA is positive. Which skin finding would be most specific for systemic lupus erythematosus?
- Malar rash sparing the nasolabial folds (Correct answer)
- Heliotrope rash
- Gottron's papules
- Erythema nodosum
Correct answer: Malar rash sparing the nasolabial folds
The malar rash of SLE classically spares the nasolabial folds, distinguishing it from rosacea and seborrheic dermatitis.
Question 7: Which of the following is the preferred treatment for onychomycosis caused by Trichophyton rubrum?
- Topical clotrimazole for 4 weeks
- Oral terbinafine for 12 weeks (Correct answer)
- Oral fluconazole for 4 weeks
- Topical ciclopirox for 48 weeks
Correct answer: Oral terbinafine for 12 weeks
Oral terbinafine for 12 weeks is the first-line treatment for toenail onychomycosis due to its superior mycological cure rates against dermatophytes.
SPEX Dermatology 4
A patient presents with a well-demarcated, erythematous plaque with silvery scale on the elbow.
The Auspitz sign is positive.
What is the most likely diagnosis?