A 5-year-old unvaccinated child presents with fever for 3 days, coryza, conjunctivitis, and a rash that started behind the ears and spread downward. The physician notes bluish-white spots on an erythematous base on the buccal mucosa opposite the lower molars. Which pathological mechanism causes the characteristic mucosal lesion?

• A Viral-induced apoptosis of basal keratinocytes causing subepithelial bullae
• B Focal necrosis of the oral mucosa with secondary bacterial superinfection
• C Immune complex deposition in the capillary walls of the oral mucosa
• D Local viral replication causing necrosis and inflammatory infiltration of the mucosal epithelium, producing focal white necrotic patches ✓

Explanation

Koplik's spots in measles are pathognomonic. Histologically, the measles virus (a paramyxovirus) directly infects oral mucosal epithelial cells, causing focal cellular necrosis with an inflammatory infiltrate; the necrotic whitish areas are surrounded by erythema. They appear before the rash and disappear rapidly once the rash appears, making them a specific early diagnostic finding. They are not immune complex-mediated or apoptotic blisters.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.