A 5-year-old presents with low-grade fever, muffled voice, and a thick grey-white membrane over the tonsils extending to the soft palate. Attempted removal of the membrane leaves a bleeding raw surface. The most likely organism is:

• A Streptococcus pyogenes
• B Corynebacterium diphtheriae ✓
• C Staphylococcus aureus
• D Haemophilus influenzae

Explanation

An adherent grey pseudomembrane that bleeds when peeled off, spreading beyond the tonsil onto the palate, is pathognomonic of diphtheritic pharyngitis caused by Corynebacterium diphtheriae. The membrane results from toxin-mediated necrosis and fibrin exudation. Streptococcal tonsillitis produces superficial exudate that wipes off easily without bleeding, which is the single fact that separates it from this presentation. Toxin production can be confirmed by the Elek test.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.