NBDE Microbiology and Pathology 4 — Questions and Answers
Question 1: A 60-year-old smoker presents with a white, non-scrapable lesion on the floor of the mouth. Biopsy shows severe epithelial dysplasia. The most appropriate management is:
- Surgical excision with close follow-up (Correct answer)
- Antifungal therapy
- Observation for 6 months
- Topical corticosteroids
Correct answer: Surgical excision with close follow-up
Severe dysplasia in a leukoplakia lesion carries high malignant transformation risk and requires surgical excision with surveillance.
Question 2: Which cytokine is primarily responsible for fever induction (endogenous pyrogen) in acute inflammatory responses?
- IL-1β (Correct answer)
- IL-4
- IL-10
- TGF-β
Correct answer: IL-1β
IL-1β (along with TNF-α and IL-6) acts on the hypothalamus to raise the body's temperature set point via prostaglandin E2 production.
Question 3: A patient develops oral ulcers, genital ulcers, and uveitis. Which condition best explains this clinical triad?
- Behçet disease (Correct answer)
- Reiter syndrome
- Pemphigus vulgaris
- Erythema multiforme
Correct answer: Behçet disease
Behçet disease is characterized by recurrent oral aphthae, genital ulcers, and ocular inflammation (uveitis) and is associated with HLA-B51.
Question 4: Osteosarcoma of the jaw most commonly affects which anatomical location?
- Posterior mandible/symphysis (Correct answer)
- Anterior maxilla
- Condylar head
- Hard palate
Correct answer: Posterior mandible/symphysis
Jaw osteosarcomas preferentially arise in the posterior body and symphysis of the mandible, occurring a decade later than long-bone osteosarcomas.
Question 5: Which immunoglobulin class is most abundant in saliva and serves as the primary mucosal defense against oral pathogens?
- Secretory IgA (sIgA) (Correct answer)
- IgG
- IgM
- IgE
Correct answer: Secretory IgA (sIgA)
Secretory IgA is produced by plasma cells in salivary glands and combines with a secretory component that protects it from proteolytic degradation in saliva.
Question 6: A 45-year-old patient on long-term corticosteroids develops an opportunistic oral infection. The most likely organism is:
- Candida albicans (Correct answer)
- Aspergillus fumigatus
- Cryptococcus neoformans
- Histoplasma capsulatum
Correct answer: Candida albicans
Oral candidiasis is the most common opportunistic infection in immunosuppressed patients, as corticosteroids impair T-cell function and local immunity.
Question 7: In which of the following conditions would you expect to find acantholysis (loss of intercellular cohesion) on biopsy?
- Pemphigus vulgaris (Correct answer)
- Mucous membrane pemphigoid
- Erythema multiforme
- Lichen planus
Correct answer: Pemphigus vulgaris
Pemphigus vulgaris is caused by IgG autoantibodies against desmoglein 3, leading to acantholysis (suprabasilar splitting) of the oral epithelium.
NBDE Microbiology and Pathology 4
A 60-year-old smoker presents with a white, non-scrapable lesion on the floor of the mouth.
Biopsy shows severe epithelial dysplasia.
The most appropriate management is: