Pharyngitis is inflammation of the throat caused primarily by viruses. Approximately 10% of cases of pharyngitis are caused by Streptococcus pyogenes (group A Streptococcus [GAS]). Streptococcal pharyngitis (strep throat) is important because poststreptococcal immune sequelae, such as rheumatic fever, may occur.
Patients will complain of sore throat that is worse when swallowing. Fever may also be present. Typical symptoms associated with an upper respiratory tract infection (rhinorrhea, sinus tenderness, ear pain, cough) may accompany the sore throat. On examination, an inflamed pharynx, tonsils, and palate are typically seen. A grayish exudate is often present on the tonsils. Tender anterior cervical lymphadenopathy may be present. Petechiae on the palate may also be a diagnostic clue for GAS (Figure 75–3).
Pharyngitis caused by Streptococcus pyogenes. Note inflamed pharynx, tonsils, and palatal petechiae. (The white circles and curved lines are an artifact of the lighting during photography.) (Used with permission from Dr. Heinz F. Eichenwald, Public Health Image Library, Centers for Disease Control and Prevention.)
S. pyogenes (GAS) is the most important bacterial cause. Group C and G streptococci also cause pharyngitis but are not antecedents to rheumatic fever. Pharyngitis caused by Neisseria gonorrhoeae is likely to be the result of sexual activity and, if it occurs in children, is considered as a sign of child abuse. Mycoplasma pneumoniae, Chlamydia pneumoniae, and Arcanobacterium haemolyticum also cause pharyngitis.
In certain countries where the diphtheria vaccine is not widely used, Corynebacterium diphtheriae is a significant cause of pharyngitis, often accompanied by a pseudomembrane. Fusobacterium necrophorum, a gram-negative anaerobe, can cause pharyngitis accompanied by septic thrombophlebitis (Lemierre’s syndrome). Note that although S. pneumoniae and H. influenzae colonize the oropharynx, they do not cause pharyngitis.
Most cases of pharyngitis are caused by respiratory viruses, such as adenovirus, influenza A and B viruses, parainfluenza virus, rhinovirus, and coronavirus. Other viral causes include Coxsackie virus (herpangina), Epstein–Barr virus (infectious mononucleosis), and herpes simplex virus, especially type 1. Human immunodeficiency virus causes an acute retroviral syndrome that includes pharyngitis as one of its components.
The main strategy in diagnostics is to establish whether there is infection with GAS. This is because GAS is treatable, and timely intervention may prevent complications such as acute rheumatic fever. The Centor criteria are criteria that may be used to aid in the diagnosis of GAS. These criteria include tonsillar exudates, tender anterior cervical adenopathy, fever, and absence of cough. Rapid antigen detection tests for GAS and throat culture are often used to confirm the diagnosis.
It can be difficult to distinguish between a bacterial pharyngitis and a viral pharyngitis when examining the throat. Figure 75–4 shows extensive exudates on the tonsils in pharyngitis caused by Epstein–Barr virus. A throat culture is the most reliable method of determining whether S. pyogenes is the cause.
Pharyngitis caused by Epstein–Barr virus. Note several whitish exudates on tonsils (red arrow). (Reproduced with permission from Kane K, Nambudiri VE, Stratigos AJ. Color Atlas & Synopsis of Pediatric Dermatology. 3rd ed. New York, NY: McGraw-Hill Education; 2017.)
If GAS is diagnosed, treatment with penicillin G, penicillin V, or amoxicillin is undertaken. In penicillin-allergic patients, erythromycin or cephalexin can be used.
The overuse of antibiotics, such as penicillin and macrolides, in cases of pharyngitis continues to be a problem. Although only 10% of sore throats are bacterial, data show that 60% of sore throats are treated with antibiotics, resulting in unnecessary expense, adverse effects, and the selection of resistant bacteria.
There is a vaccine against C. diphtheriae and influenza virus but not against pharyngitis caused by S. pyogenes or any other bacterial or viral cause. Long-term carriers of GAS should not be treated because there is no evidence that such treatment prevents spread of the organism to close contacts or the development of complications such as acute rheumatic fever. Note that children who have rheumatic heart disease should receive penicillin orally for many years to prevent infection by S. pyogenes, which could cause a flare of their rheumatic heart disease.