1. Diphtheria (Corynebacterium diphtheriae)

   • Classic Presentation: Thick, adherent gray-white pseudomembrane over the tonsils and pharynx.

   • Context: Rare in vaccinated populations; consider in unvaccinated individuals or regions with low vaccination rates. Associated with systemic toxicity and respiratory compromise.

2. Streptococcal Pharyngitis (Group A Streptococcus)

   • Typical Features: White or yellow exudates, but may appear grayish. Accompanied by fever, swollen tonsils, and absence of cough. (杨梅舌)

   • Diagnosis: Rapid antigen test or throat culture.

3. Vincent’s Angina (Necrotizing Ulcerative Gingivitis/Stomatitis)

   • Presentation: Grayish exudate over ulcerated tonsils or gingiva, often with foul breath and pain. Caused by Fusobacterium spp. and spirochetes.

   • Risk Factors: Poor oral hygiene, malnutrition, or immunosuppression.

4. Infectious Mononucleosis (Epstein-Barr Virus)

   • Exudates: Typically white or yellowish, but severe cases may appear grayish. Associated with fatigue, lymphadenopathy, and hepatosplenomegaly.

   • Diagnosis: Monospot test or EBV serology.

5. Candidiasis (Oral Thrush)

   • Features: Creamy white patches that can extend to the tonsils; scrapable but may appear grayish in immunocompromised patients (e.g., HIV, diabetes).