Pharyngitis

Etiology

About 50% to 80% of pharyngitis, or sore throat, symptoms are viral in origin and include a variety of viral pathogens. These pathogens are predominantly rhinovirus, influenza, adenovirus, coronavirus, and parainfluenza. Less common viral pathogens include herpes, Epstein-Barr virus, human immunodeficiency virus (HIV), and coxsackievirus. More severe cases tend to be bacterial and may develop after an initial viral infection.

The most common bacterial infection is Group A beta-hemolytic streptococci, which causes 5% to 36% of cases of acute pharyngitis. Other bacterial etiologies include Group B & C streptococci, Chlamydia pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Candida, Neisseria meningitidis, Neisseria gonorrhoeae, Arcanobacterium haemolyticum, Fusobacterium necrophorum, and Corynebacterium diphtheriae. Environmental allergies and chemical exposures may also cause acute pharyngitis.

Pharyngitis symptoms may also be part of the symptom complexes of other serious illnesses, including peritonsillar abscess, retropharyngeal abscess, epiglottitis, and Kawasaki disease.[3][4]

Epidemiology

In 2010, there were 1.814 million emergency department visits for pharyngitis, of which 692,000 were for patients under the age of 15. Most cases of pharyngitis occur in children under the age of 5. Adults can also develop the disorder but at a lower rate. Globally, pharyngitis rates are very high chiefly in countries where antibiotics are overprescribed.[5][6]

Pathophysiology

Bacteria and viruses can cause direct invasion of the pharyngeal mucosa. Certain viruses like rhinovirus can cause irritation secondary to nasal secretions. In almost all cases, there is a local invasion of the pharyngeal mucosa which also results in excess secretion and edema.

History and Physical

The history and physical examination should look for findings consistent with uncomplicated pharyngitis and exclude other potentially serious and life-threatening illnesses. Clinical manifestations frequently include fever, tonsillar exudates, painful cervical adenopathy, pharyngeal erythema, and ear pain. Uncomplicated infectious pharyngitis, both viral and bacterial, typically is self-limited to 5 to 7 days, is not progressive, is bilateral, does not have trismus, and does not have evidence of airway obstruction (stridor).[7] 

If viral in etiology, associated symptoms often include coughing, rhinorrhea, conjunctivitis, headache, and a rash. Group A beta-hemolytic streptococcal pharyngitis typically has an acute onset, lacks signs of a viral upper respiratory infection such as a cough or rhinorrhea, and is associated with fever, tonsillar exudates, and cervical adenopathy. Pharyngitis due to the Epstein-Barr virus, otherwise known as infectious mononucleosis,  can cause headaches, fever, tonsillar hypertrophy, lymphocytosis, and atypical lymphocytes. Myalgia and fatigue are commonly reported symptoms. Infectious mononucleosis can have both anterior and posterior cervical lymphadenopathy. Patients can have persistent lymphadenopathy and fatigue for up to 3 weeks. It is important to assess for hepatomegaly or splenomegaly. If a morbilliform rash develops after amoxicillin for presumed Group A beta-hemolytic streptococci, infectious mononucleosis should be suspected.

A retropharyngeal abscess is characterized by neck stiffness and pain with neck extension. For epiglottitis, look for stridor as a symptom. F. necrophorum is the bacterium that causes Lemierre's syndrome, or internal jugular vein thrombophlebitis. If there has been orogenital contact by the patient, consider N. gonorrhoeae. An acute retroviral syndrome due to HIV may be associated with fever and non-exudative pharyngitis.

Evaluation

A variety of clinical decision rules have been developed to improve the diagnosis of Group A beta-hemolytic streptococcal pharyngitis and to guide testing and treatment. The Centor Score is one of the most commonly used, particularly for adult patients.[8][9]

Centor Criteria (1 point for each) for Group A Beta-hemolytic Streptococci:

1. Tonsillar exudate
2. Tender anterior cervical left mentoanterior
3. History of fever
4. Absence of a cough

More likely in 5 to 15 years of age and not valid under 3 years old.

Point Totals and Recommended Actions: 

• 0-1: No testing or antibiotics
• 2-3: Rapid antigen test
• 4: No testing, empiric antibiotics

White blood cell counts have minimal value in the differentiation of viral versus bacterial etiologies of pharyngitis. A lymphocytosis (greater than 50%) or increased atypical lymphocytes (greater than 10%) may suggest infectious mononucleosis.

Rapid antigen detection tests (RADT) are very specific for Group A beta-hemolytic streptococci, but their sensitivity varies widely, from about 70% to 90%. If the test is positive, treatment should be initiated. If it is negative, particularly in children, a throat culture should be obtained and should guide treatment.

Throat cultures have been the ideal standard for diagnosis, but their sensitivity is variable and is influenced by many factors. These factors include the bacterial burden, site of collection (the tonsillar surface is best), culture medium, and culture atmosphere.

A heterophile antibody or monospot test is 70% to 92% sensitive and 96% to 100% specific. This test for infectious mononucleosis is commonly available, but the ideal standard is to use Epstein-Barr virus serology. The test's sensitivity is lessened by testing early in the course of the illness (1 to 2 weeks) and by the age of the patient (less than 12 years).

For gonococcal detection, a culture should be obtained. Thayer-Martin agar is most commonly used. For Candida, test with a potassium hydroxide preparation or Sabouraud agar. 

A chest X-ray is not needed for routine cases. If airway compromise is suspected, a lateral neck X-ray should be obtained.

A computed tomography (CT) scan may help identify a peritonsillar abscess.

Treatment / Management

Antibiotics for pharyngitis are usually used for patients with Group A beta-hemolytic streptococcal pharyngitis. Antibiotics may shorten the duration of symptoms by 16 to 24 hours and prevent rheumatic fever, which older data suggest occur in 1 in 400 untreated cases of strep pharyngitis. Antibiotics should only be used for Group A beta-hemolytic streptococci-positive patients, particularly if they are children, based on a positive culture or a rapid antigen detection test. A 10-day course of oral penicillin is recommended to ensure the eradication of bacterial carriage and the prevention of rheumatic fever.[1][10][11][12](B3)

Treatment options for Group A beta-hemolytic streptococcal pharyngitis include oral treatment with penicillin V or oral amoxicillin. Cephalosporins, macrolides, and clindamycin may also be used. Intramuscular penicillin is also a treatment option. Resistance may develop during treatment with azithromycin and clarithromycin, and it is not considered a first-line antibiotic for this indication. In patients with a mild penicillin allergy, cephalosporins can be used. In patients with a history of anaphylaxis to penicillin, azithromycin or clindamycin can be used. The disease is no longer infectious after 24 hours of antibiotics.[13](B2)

Single-dose corticosteroids like dexamethasone may be given to reduce the severity of symptoms, although the evidence for this approach is limited. Symptomatic treatment with gargles and acetaminophen or nonsteroidal anti-inflammatory drugs should be recommended. Use caution in the setting of severe dehydration. For patients with infectious mononucleosis, contact sports should be avoided for 6 to 8 weeks due to the risk of splenic rupture.

Differential Diagnosis

• Airway obstruction from any cause
• Allergic rhinitis
• Cancer of the head and neck
• Gastroesophageal reflux disease
• Peritonsillar abscess
• Diphtheria
• Epiglottitis
• Herpes simplex virus
• Mononucleosis

Prognosis

In general, the prognosis for pharyngitis is good as both viral and bacterial infections are typically self-limited to 5 to 7 days.

In developing countries, over 20 million individuals are affected by group A streptococci and develop acute rheumatic fever. This disorder is the leading cause of death in young people.  Mortality from pharyngitis is rare but does occur if the airway is compromised.

Most cases of pharyngitis resolve within 7 to 10 days. Treatment failures are usually due to antibiotic resistance, poor compliance, and untreated close contacts.

Complications

Complications of bacterial pharyngitis include:

• Epiglottitis
• Otitis media
• Mastoiditis
• Sinusitis
• Acute rheumatic fever
• Post-streptococcal glomerulonephritis
• Toxic shock syndrome