Mononucleosis vs Streptococcal pharyngitis
How to tell Mononucleosis and Streptococcal pharyngitis apart when a board question makes them look alike.
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Posterior cervical lymphadenopathy with atypical lymphocytosis points to mononucleosis.
Side by side
Exudative pharyngitis with prominent fatigue, posterior cervical lymphadenopathy, and atypical lymphocytosis suggesting Epstein-Barr virus infection.
Acute sore throat with fever, tonsillar exudates, tender anterior cervical nodes, and positive group A streptococcal testing.
Primary EBV infection of B cells triggers intense cytotoxic T-cell response with systemic lymphoid enlargement.
Group A streptococcal invasion of pharyngeal mucosa causes suppurative inflammation and immune-mediated sequelae risk.
Heterophile antibody test is usually positive after the first week, CBC shows atypical lymphocytes often above 10%, and mild transaminitis may be present.
Rapid antigen detection or throat culture confirms group A streptococcus; neutrophilic leukocytosis may occur, and atypical lymphocytosis is usually absent.
The trap
Exudative tonsillitis can look identical at first glance, so some patients with mono receive aminopenicillins and then develop a diffuse rash. The resolving clues are posterior node predominance, hepatosplenomegaly, marked fatigue, and atypical lymphocytes, while true streptococcal disease is confirmed by rapid testing and treated with narrow-spectrum antibiotics.
The repair move
Next best step: confirm suspected streptococcal infection with rapid antigen testing before antibiotics when presentation overlaps, and when mononucleosis is likely provide supportive care, avoid contact sports for at least 3 to 4 weeks or until spleen risk resolves, and avoid amoxicillin or ampicillin due to rash risk.
Try a free question
CoreA 17-year-old girl has sore throat, fever, fatigue, posterior cervical lymphadenopathy, and mild splenomegaly. BP 112/70 mm Hg, HR 94/min, temp 38.1 C. CBC shows atypical lymphocytes. What is the next best step in management?
Show answer and explanation
Answer: B. Provide supportive care and restrict contact sports. This pattern is classic for mononucleosis, which is treated supportively with counseling to reduce splenic injury risk.
Why the other choices are tempting
- A. Wrong. Aminopenicillins can cause rash in EBV and are not indicated.
- C. Wrong. Tonsillectomy is not first-line for acute EBV pharyngitis.
- D. Wrong. Oseltamivir treats influenza, not EBV.
- E. Wrong. Broad-spectrum antibiotics are unnecessary in viral mononucleosis.
Flashcards
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Which lymph node distribution favors infectious mononucleosis over streptococcal pharyngitis?
Posterior cervical lymphadenopathy favors mononucleosis.
What blood-smear clue supports mononucleosis diagnosis?
Atypical lymphocytosis, often above 10%, supports EBV mononucleosis.
Quick answers
What is the fastest way to tell Mononucleosis from Streptococcal pharyngitis?
Posterior cervical lymphadenopathy with atypical lymphocytosis points to mononucleosis.
What is the key clue for Mononucleosis?
Exudative pharyngitis with prominent fatigue, posterior cervical lymphadenopathy, and atypical lymphocytosis suggesting Epstein-Barr virus infection.
What is the key clue for Streptococcal pharyngitis?
Acute sore throat with fever, tonsillar exudates, tender anterior cervical nodes, and positive group A streptococcal testing.
What is the common trap with Mononucleosis vs Streptococcal pharyngitis?
Exudative tonsillitis can look identical at first glance, so some patients with mono receive aminopenicillins and then develop a diffuse rash. The resolving clues are posterior node predominance, hepatosplenomegaly, marked fatigue, and atypical lymphocytes, while true streptococcal disease is confirmed by rapid testing and treated with narrow-spectrum antibiotics.