NR5 NR511 Differential Diagnosis — Midterm Practice Exam • 100 Questions with Answers &
Rationales
11
Question 1 of 100
A 34-year-old female presents with a 3-day history of pruritic, erythematous vesicles on an
erythematous base distributed in a dermatomal pattern along her left thorax. She reports a
burning sensation that preceded the rash by 2 days. Which of the following is the most likely
diagnosis?
A. Contact dermatitis
B. Herpes zoster
C. Impetigo
D. Bullous pemphigoid
Correct Answer
B. Herpes zoster
Rationale
Herpes zoster (shingles) presents with prodromal pain/burning followed by a
dermatomal vesicular rash on an erythematous base. The unilateral dermatomal
distribution is the hallmark distinguishing feature. Contact dermatitis is bilateral and
related to allergen exposure; impetigo presents with honey-crusted lesions; bullous
pemphigoid produces large tense bullae.
,Question 2 of 100
A 22-year-old male presents with comedones, inflammatory papules, and pustules on his face
and upper back. He has tried over-the-counter benzoyl peroxide without improvement. Which
is the most appropriate next step in management?
A. Oral isotretinoin
B. Topical retinoid plus topical antibiotic
C. Systemic corticosteroids
D. Antifungal cream
Correct Answer
B. Topical retinoid plus topical antibiotic
Rationale
Moderate acne vulgaris not responding to OTC benzoyl peroxide is treated with a
combination of topical retinoid and topical antibiotic (e.g., tretinoin + clindamycin). Oral
isotretinoin is reserved for severe, nodular, or treatment-resistant acne. Corticosteroids
worsen acne; antifungals are not indicated.
,Question 3 of 100
A patient presents with a well-demarcated, salmon-colored plaque with silvery scales on the
extensor surface of the elbows and knees. The patient also reports nail pitting. What is the
most likely diagnosis?
A. Eczema
B. Psoriasis
C. Tinea corporis
D. Seborrheic dermatitis
Correct Answer
B. Psoriasis
Rationale
Psoriasis classically presents with well-demarcated plaques with silvery scales on
extensor surfaces, and nail pitting is a common associated finding. Eczema typically
affects flexural areas; tinea corporis has central clearing; seborrheic dermatitis affects
oily areas like the scalp and face.
, Question 4 of 100
A 45-year-old presents with a pigmented lesion with irregular borders, multiple colors (brown,
black, red), and a diameter of 8mm. Which feature is most concerning for melanoma?
A. Round border
B. Uniform brown color
C. Diameter greater than 6mm
D. Flat surface
Correct Answer
C. Diameter greater than 6mm
Rationale
The ABCDE criteria for melanoma include Asymmetry, Border irregularity, Color
variation, Diameter >6mm, and Evolution. A diameter greater than 6mm is one of the
warning signs for melanoma. The other options describe benign characteristics.
Rationales
11
Question 1 of 100
A 34-year-old female presents with a 3-day history of pruritic, erythematous vesicles on an
erythematous base distributed in a dermatomal pattern along her left thorax. She reports a
burning sensation that preceded the rash by 2 days. Which of the following is the most likely
diagnosis?
A. Contact dermatitis
B. Herpes zoster
C. Impetigo
D. Bullous pemphigoid
Correct Answer
B. Herpes zoster
Rationale
Herpes zoster (shingles) presents with prodromal pain/burning followed by a
dermatomal vesicular rash on an erythematous base. The unilateral dermatomal
distribution is the hallmark distinguishing feature. Contact dermatitis is bilateral and
related to allergen exposure; impetigo presents with honey-crusted lesions; bullous
pemphigoid produces large tense bullae.
,Question 2 of 100
A 22-year-old male presents with comedones, inflammatory papules, and pustules on his face
and upper back. He has tried over-the-counter benzoyl peroxide without improvement. Which
is the most appropriate next step in management?
A. Oral isotretinoin
B. Topical retinoid plus topical antibiotic
C. Systemic corticosteroids
D. Antifungal cream
Correct Answer
B. Topical retinoid plus topical antibiotic
Rationale
Moderate acne vulgaris not responding to OTC benzoyl peroxide is treated with a
combination of topical retinoid and topical antibiotic (e.g., tretinoin + clindamycin). Oral
isotretinoin is reserved for severe, nodular, or treatment-resistant acne. Corticosteroids
worsen acne; antifungals are not indicated.
,Question 3 of 100
A patient presents with a well-demarcated, salmon-colored plaque with silvery scales on the
extensor surface of the elbows and knees. The patient also reports nail pitting. What is the
most likely diagnosis?
A. Eczema
B. Psoriasis
C. Tinea corporis
D. Seborrheic dermatitis
Correct Answer
B. Psoriasis
Rationale
Psoriasis classically presents with well-demarcated plaques with silvery scales on
extensor surfaces, and nail pitting is a common associated finding. Eczema typically
affects flexural areas; tinea corporis has central clearing; seborrheic dermatitis affects
oily areas like the scalp and face.
, Question 4 of 100
A 45-year-old presents with a pigmented lesion with irregular borders, multiple colors (brown,
black, red), and a diameter of 8mm. Which feature is most concerning for melanoma?
A. Round border
B. Uniform brown color
C. Diameter greater than 6mm
D. Flat surface
Correct Answer
C. Diameter greater than 6mm
Rationale
The ABCDE criteria for melanoma include Asymmetry, Border irregularity, Color
variation, Diameter >6mm, and Evolution. A diameter greater than 6mm is one of the
warning signs for melanoma. The other options describe benign characteristics.
