Pathology · single question
A patient presents with small, painful ulcers on one side of the face and lips following endodontic treatment. One of the ulcers appears black. What is the MOST likely diagnosis?
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Correct answer: A. Necrotizing fasciitis
Necrotizing fasciitis of the head and neck is a rare but life-threatening deep soft tissue infection. A key clue here is the unilateral distribution, post-endodontic setting, and the black ulcer (necrotic tissue) — classic for tissue necrosis. This contrasts with aphthous ulcers (bilateral, no necrotic tissue), herpes zoster (dermatomal vesicles), or drug reactions (bilateral, often systemic). Necrotizing fasciitis requires emergency surgical debridement and IV antibiotics.
- A. ✅ CORRECT – The combination of unilateral ulcers after dental treatment with a black (necrotic) ulcer at the corner of the lip is characteristic of necrotizing fasciitis.
- B. ❌ Aphthous ulcers are small round/oval ulcers with yellow pseudomembrane and red halo — they are bilateral, not post-procedural, and never appear black.
- C. ❌ Drug reactions can cause ulcers/stomatitis but typically present bilaterally, symmetrically, and without tissue necrosis.
- D. ❌ Herpes zoster (shingles) presents as a unilateral dermatomal vesicular rash — vesicles, not necrotic black ulcers, and not directly triggered by dental procedures.