ABD Cutaneous Infectious Diseases 2 — Questions and Answers
Question 1: A 6-year-old presents with honey-colored crusted lesions around the nose and mouth. What is the most likely diagnosis?
- Non-bullous impetigo (Correct answer)
- Ecthyma gangrenosum
- Erysipelas
- Perioral dermatitis
Correct answer: Non-bullous impetigo
Honey-colored crusts around the mouth and nose in a child are classic for non-bullous impetigo, usually caused by Staphylococcus aureus or Streptococcus pyogenes.
Question 2: Which organism is the most common cause of bullous impetigo?
- Streptococcus pyogenes
- Staphylococcus aureus (Correct answer)
- Pseudomonas aeruginosa
- Corynebacterium minutissimum
Correct answer: Staphylococcus aureus
Bullous impetigo is caused by exfoliative toxin-producing Staphylococcus aureus, which cleaves desmoglein 1.
Question 3: A diabetic patient develops a rapidly spreading, exquisitely painful erythema with crepitus and dishwater-gray drainage. What is the priority intervention?
- Topical mupirocin
- Oral cephalexin and observation
- Urgent surgical debridement (Correct answer)
- Warm compresses only
Correct answer: Urgent surgical debridement
Pain out of proportion, crepitus, and gray drainage suggest necrotizing fasciitis, a surgical emergency requiring immediate debridement.
Question 4: Erythrasma of the intertriginous areas fluoresces what color under Wood's lamp?
- Blue-green
- Coral-red (Correct answer)
- Yellow-green
- Bright white
Correct answer: Coral-red
Corynebacterium minutissimum produces coproporphyrin III, causing coral-red fluorescence under Wood's lamp.
Question 5: A febrile patient has a sharply demarcated, raised, warm, erythematous plaque on the face. This presentation is most consistent with:
- Cellulitis
- Erysipelas (Correct answer)
- Contact dermatitis
- Angioedema
Correct answer: Erysipelas
Erysipelas involves the superficial dermis and lymphatics, producing a sharply demarcated, raised plaque, most often from Streptococcus pyogenes.
Question 6: Which finding is characteristic of staphylococcal scalded skin syndrome (SSSS)?
- Positive Nikolsky sign with sparing of mucous membranes (Correct answer)
- Mucosal involvement with target lesions
- Deep dermal necrosis
- Grouped vesicles on an erythematous base
Correct answer: Positive Nikolsky sign with sparing of mucous membranes
SSSS shows a positive Nikolsky sign and characteristically spares the mucous membranes, distinguishing it from toxic epidermal necrolysis.
Question 7: First-line treatment for a small, uncomplicated cutaneous abscess is:
- Systemic vancomycin
- Incision and drainage (Correct answer)
- Topical corticosteroids
- Oral fluconazole
Correct answer: Incision and drainage
Incision and drainage is the primary treatment for a simple cutaneous abscess, with antibiotics reserved for surrounding cellulitis or systemic signs.
ABD Cutaneous Infectious Diseases 2
A 6-year-old presents with honey-colored crusted lesions around the nose and mouth.
What is the most likely diagnosis?