NR-511 Exam
Differential Diagnosis & Primary Care Practicum
Midterm and Final Exam Questions with Answers & Rationales
1. A 45-year-old presents with a single, well-demarcated, erythematous
plaque with silvery scale on the extensor surface of the elbow. What is
the most likely diagnosis?
A. Psoriasis
B. Eczema (atopic dermatitis)
C. Tinea corporis
D. Seborrheic dermatitis
Answer: A
Rationale: Psoriasis classically presents as well-demarcated erythematous
plaques with silvery scale on extensor surfaces (elbows, knees); eczema
favors flexural areas and lacks the thick silvery scale.
2. Which historical feature best distinguishes tinea corporis from
nummular eczema?
A. Central clearing with an active, scaly border in tinea
B. Intense itching present only in tinea
C. Nummular eczema always has a KOH-positive scraping
D. Tinea corporis lesions are never pruritic
Answer: A
Rationale: Tinea corporis classically shows an annular lesion with central
clearing and an active, raised, scaly border, whereas nummular eczema
presents as coin-shaped plaques without central clearing.
,3. A patient presents with grouped vesicles on an erythematous base in
a unilateral dermatomal distribution with burning pain. What is the most
likely diagnosis?
A. Herpes zoster
B. Contact dermatitis
C. Impetigo
D. Molluscum contagiosum
Answer: A
Rationale: Herpes zoster (shingles) presents as grouped vesicles on an
erythematous base following a dermatomal distribution, often preceded by
pain or paresthesia in that dermatome.
4. What is the first-line pharmacologic treatment for mild acne vulgaris
with primarily comedonal lesions?
A. Topical retinoid
B. Oral isotretinoin
C. Oral antibiotics
D. Systemic corticosteroids
Answer: A
Rationale: Topical retinoids are first-line for comedonal acne because they
normalize follicular keratinization; oral isotretinoin and systemic therapies are
reserved for more severe or resistant cases.
5. A honey-colored crusted lesion around the mouth of a child is most
consistent with which diagnosis?
A. Impetigo
B. Herpes simplex
C. Perioral dermatitis
D. Atopic dermatitis
Answer: A
Rationale: Impetigo classically presents with honey-colored crusted lesions,
most often caused by Staphylococcus aureus or Streptococcus pyogenes,
commonly around the nose and mouth in children.
,6. Which feature of a pigmented skin lesion should raise the most
concern for melanoma?
A. Asymmetry, irregular Border, color Variation, Diameter >6mm,
Evolution (ABCDE criteria)
B. Uniform round shape with even color
C. Lesion present unchanged for over 10 years
D. Diameter less than 3mm with symmetric borders
Answer: A
Rationale: The ABCDE criteria (Asymmetry, Border irregularity, Color
variation, Diameter >6mm, Evolution/change over time) are used to identify
lesions suspicious for melanoma and warranting biopsy/referral.
7. A patient with a red, painful, swollen area of skin with
well-demarcated raised borders and systemic fever is most consistent
with which diagnosis?
A. Erysipelas
B. Cellulitis
C. Contact dermatitis
D. Venous stasis dermatitis
Answer: A
Rationale: Erysipelas is a superficial skin infection with sharply demarcated,
raised borders (distinguishing it from cellulitis, which has less-defined borders
and involves deeper tissue) and is often accompanied by fever.
8. A 6-year-old presents with pruritic, excoriated papules in the
interdigital web spaces and wrists, with similar symptoms in other
household members. What is the most likely diagnosis?
A. Scabies
B. Atopic dermatitis
C. Pediculosis
D. Contact dermatitis
Answer: A
Rationale: Scabies classically presents with intensely pruritic
papules/burrows in the web spaces, wrists, and flexural areas, and often
, affects multiple household members due to close-contact transmission.
9. Which is the most common cause of acute otitis media in children?
A. Streptococcus pneumoniae
B. Staphylococcus aureus
C. Pseudomonas aeruginosa
D. Candida albicans
Answer: A
Rationale: Streptococcus pneumoniae is historically the most common
bacterial cause of acute otitis media, followed by nontypeable Haemophilus
influenzae and Moraxella catarrhalis.
10. On otoscopic exam, a bulging, erythematous tympanic membrane
with loss of landmarks and decreased mobility supports which
diagnosis?
A. Acute otitis media
B. Otitis externa
C. Otitis media with effusion (without acute infection)
D. Cholesteatoma
Answer: A
Rationale: Acute otitis media is characterized by a bulging, erythematous,
poorly mobile tympanic membrane, differentiating it from otitis media with
effusion, which typically shows a retracted or neutral, non-erythematous
membrane.
11. A patient presents with ear pain worsened by traction on the pinna,
along with a swollen, erythematous ear canal. What is the most likely
diagnosis?
A. Otitis externa
B. Acute otitis media
C. Mastoiditis
D. Temporomandibular joint dysfunction
Answer: A
Differential Diagnosis & Primary Care Practicum
Midterm and Final Exam Questions with Answers & Rationales
1. A 45-year-old presents with a single, well-demarcated, erythematous
plaque with silvery scale on the extensor surface of the elbow. What is
the most likely diagnosis?
A. Psoriasis
B. Eczema (atopic dermatitis)
C. Tinea corporis
D. Seborrheic dermatitis
Answer: A
Rationale: Psoriasis classically presents as well-demarcated erythematous
plaques with silvery scale on extensor surfaces (elbows, knees); eczema
favors flexural areas and lacks the thick silvery scale.
2. Which historical feature best distinguishes tinea corporis from
nummular eczema?
A. Central clearing with an active, scaly border in tinea
B. Intense itching present only in tinea
C. Nummular eczema always has a KOH-positive scraping
D. Tinea corporis lesions are never pruritic
Answer: A
Rationale: Tinea corporis classically shows an annular lesion with central
clearing and an active, raised, scaly border, whereas nummular eczema
presents as coin-shaped plaques without central clearing.
,3. A patient presents with grouped vesicles on an erythematous base in
a unilateral dermatomal distribution with burning pain. What is the most
likely diagnosis?
A. Herpes zoster
B. Contact dermatitis
C. Impetigo
D. Molluscum contagiosum
Answer: A
Rationale: Herpes zoster (shingles) presents as grouped vesicles on an
erythematous base following a dermatomal distribution, often preceded by
pain or paresthesia in that dermatome.
4. What is the first-line pharmacologic treatment for mild acne vulgaris
with primarily comedonal lesions?
A. Topical retinoid
B. Oral isotretinoin
C. Oral antibiotics
D. Systemic corticosteroids
Answer: A
Rationale: Topical retinoids are first-line for comedonal acne because they
normalize follicular keratinization; oral isotretinoin and systemic therapies are
reserved for more severe or resistant cases.
5. A honey-colored crusted lesion around the mouth of a child is most
consistent with which diagnosis?
A. Impetigo
B. Herpes simplex
C. Perioral dermatitis
D. Atopic dermatitis
Answer: A
Rationale: Impetigo classically presents with honey-colored crusted lesions,
most often caused by Staphylococcus aureus or Streptococcus pyogenes,
commonly around the nose and mouth in children.
,6. Which feature of a pigmented skin lesion should raise the most
concern for melanoma?
A. Asymmetry, irregular Border, color Variation, Diameter >6mm,
Evolution (ABCDE criteria)
B. Uniform round shape with even color
C. Lesion present unchanged for over 10 years
D. Diameter less than 3mm with symmetric borders
Answer: A
Rationale: The ABCDE criteria (Asymmetry, Border irregularity, Color
variation, Diameter >6mm, Evolution/change over time) are used to identify
lesions suspicious for melanoma and warranting biopsy/referral.
7. A patient with a red, painful, swollen area of skin with
well-demarcated raised borders and systemic fever is most consistent
with which diagnosis?
A. Erysipelas
B. Cellulitis
C. Contact dermatitis
D. Venous stasis dermatitis
Answer: A
Rationale: Erysipelas is a superficial skin infection with sharply demarcated,
raised borders (distinguishing it from cellulitis, which has less-defined borders
and involves deeper tissue) and is often accompanied by fever.
8. A 6-year-old presents with pruritic, excoriated papules in the
interdigital web spaces and wrists, with similar symptoms in other
household members. What is the most likely diagnosis?
A. Scabies
B. Atopic dermatitis
C. Pediculosis
D. Contact dermatitis
Answer: A
Rationale: Scabies classically presents with intensely pruritic
papules/burrows in the web spaces, wrists, and flexural areas, and often
, affects multiple household members due to close-contact transmission.
9. Which is the most common cause of acute otitis media in children?
A. Streptococcus pneumoniae
B. Staphylococcus aureus
C. Pseudomonas aeruginosa
D. Candida albicans
Answer: A
Rationale: Streptococcus pneumoniae is historically the most common
bacterial cause of acute otitis media, followed by nontypeable Haemophilus
influenzae and Moraxella catarrhalis.
10. On otoscopic exam, a bulging, erythematous tympanic membrane
with loss of landmarks and decreased mobility supports which
diagnosis?
A. Acute otitis media
B. Otitis externa
C. Otitis media with effusion (without acute infection)
D. Cholesteatoma
Answer: A
Rationale: Acute otitis media is characterized by a bulging, erythematous,
poorly mobile tympanic membrane, differentiating it from otitis media with
effusion, which typically shows a retracted or neutral, non-erythematous
membrane.
11. A patient presents with ear pain worsened by traction on the pinna,
along with a swollen, erythematous ear canal. What is the most likely
diagnosis?
A. Otitis externa
B. Acute otitis media
C. Mastoiditis
D. Temporomandibular joint dysfunction
Answer: A
