Pharyngitis

Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Determining the causative agent based on symptoms alone is difficult. Thus, a throat swab is often performed to rule out a bacterial cause. The mainstay of treatment is symptomatic and supportive, with bacterial causes requiring antibiotics.

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Etiology

Pharyngitis is defined as inflammation of the pharynx and surrounding structures.

Most cases are due to an infectious organism acquired from close contact with an infected individual.

  • Viral:
    • Adenovirus (most common) 
    • Coxsackie A virus
    • Orthomyxoviridae family
    • Epstein-Barr virus (causes infectious mononucleosis)
    • Herpes simplex virus
    • Measles virus
    • Rhinovirus
    • Coronavirus
    • Respiratory syncytial virus
    • Parainfluenza virus
  • Bacterial:
    • Streptococcus pyogenes (most frequent bacterial cause of infectious pharyngitis)
    • Streptococcus pneumoniae (beta-hemolytic Streptococcus infections are common in children aged 4–7 years)
    • Haemophilus influenzae
    • Bordetella pertussis
    • Bacillus anthracis
    • Corynebacterium diphtheriae
    • Neisseria gonorrhoeae
    • Chlamydophila pneumoniae
    • Mycoplasma pneumoniae
    • Fusobacterium necrophorum
  • Fungal:
    • Candidiasis (oral thrush involving pharynx can occur in immunocompromised patients, with antibiotic and inhaled glucocorticoid use, and in patients receiving chemotherapy and/or radiation)
  • Non-infectious causes:
    • Smoking
    • Snoring
    • Shouting
    • Tracheal intubation
    • Medications
    • Concomitant illness
    • Indoor and outdoor air pollutants
    • Temperature and humidity (e.g., dryness during winter months, forced-air heating)
    • Hazardous or occupational irritants
    • Foreign body (e.g., fishbone embedded in the pharynx)
    • Systemic inflammatory conditions: Kawasaki disease, Stevens-Johnson syndrome, Behçet’s syndrome, PFAPA (periodic fever, aphthous stomatitis, pharyngitis, adenitis) syndrome
    • Chemical exposure (e.g., paraquat, alkali)
    • Referred pain (e.g., otitis media, tooth abscess)
    • Psychogenic

Clinical Presentation

  • Symptoms usually last 3–5 days
  • Throat discomfort
  • Odynophagia: painful swallowing
  • Dry cough
  • Cervical lymphadenopathy
  • Pharyngeal exudate
  • No cough or hoarseness (points toward laryngitis if these symptoms are present)
  • Constitutional symptoms: body aches, headache, fever, myalgia, malaise, abrupt onset

Diagnosis

Centor score: estimates the probability that pharyngitis is streptococcal and suggests management course for adults

  • Criteria:
    • Age 3–14 years: +1
    • Age 15–44 years: +0
    • Age ≥ 45 years: –1
    • Absence of cough: +1
    • Tonsillar exudates: +1
    • Fever: +1
    • Tender anterior cervical adenopathy: +1
  • Scoring:
    • –1, 0, or 1 point: no further testing or antibiotics
    • 2 points: optional rapid strep testing and/or culture
    • 3 points: rapid strep test and/or culture recommended, antibiotics only if positive
    • 4 or 5 points: rapid strep testing and/or culture with empiric antibiotics recommended

Laboratory diagnosis:

  • Rapid strep test: detects ribonuclease antigen
  • Throat swab for culture 
  • Serological testing

Identification of beta-hemolytic streptococcal infection is of paramount importance as it is associated with the development of rheumatic heart disease if left untreated.

Diagnostic algorithm for pharyngitis

Diagnostic algorithm for pharyngitis

Image by Lecturio.

To recall the Centor criteria, remember:

  • C = cough 
  • E = exudate
  • N = nodes
  • T = temperature (fever)
  • OR = young OR old modifier

Management

  • The mainstay of treatment is symptomatic and supportive:
    • Adequate fluid intake, avoidance of respiratory irritants such as smoke, avoidance of acidic foods and beverages, soft diet, adequate rest, systemic analgesia, medicated lozenges, and throat spray
  • Some patients may require antibiotics for laboratory-documented bacterial pharyngitis:
    • Treat pharyngitis due to group A beta-hemolytic Streptococci with oral penicillin or amoxicillin for 10 days (cephalexin if penicillin causes rash; clindamycin or macrolide if penicillin causes anaphylaxis).
    • Timely treatment is crucial for the prevention of acute rheumatic fever.
  • Viral pharyngitis is self-limiting and resolves spontaneously and steadily within a few days without worsening.
  • If there is an underlying cause, identify and treat it (e.g., retroviral therapy for HIV, penicillin for Group A Streptococcus, nystatin for Candida, etc.).

Complications

Suppurative complications

  • Sinusitis
  • Otitis media
  • Epiglottitis
  • Mastoiditis
  • Peritonsillar abscess
  • Retropharyngeal abscess
  • Suppurative cervical lymphadenitis
  • Pneumonia
  • Tonsillar cellulitis
  • Necrotizing fasciitis
  • Streptococcal bacteremia (rare)
  • Meningitis or brain abscess (extremely rare)

Non-suppurative complications

  • Airway obstruction
  • Thrombocytopenia
  • Myocarditis
  • Pericarditis
  • Encephalitis
  • Meningitis
  • Toxic shock syndrome
  • Acute rheumatic fever
  • Acute inflammatory demyelinating polyneuropathy
  • Poststreptococcal reactive arthritis
  • Acute glomerulonephritis
  • PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections)

Differential Diagnosis

The following conditions are differential diagnoses of pharyngitis:

  • Epiglottitis: an inflammation of the epiglottis caused by Haemophilus, streptococcal, or staphylococcal infections, which manifests with difficulty in breathing, stridor, and cyanosis ultimately leading to death due to obstruction of airways
  • Laryngitis or laryngotracheitis: an inflammation of the larynx due to trauma or infection, among other causes. In this condition, the 2 folds of mucous membrane that make up the vocal cords become inflamed and irritated. 
  • Peritonsillar abscess: a deep neck infection that commonly occurs in adolescents or young adults as a complication of acute tonsillitis. Presents with fever, sore throat, dysphagia, so-called “hot-potato” voice, and trismus
  • Candidiasis: a fungal infection caused by Candida yeasts that can cause infections deep within the body, affecting internal organs such as the kidney, heart, or brain
  • Diphtheria: a serious bacterial infection caused by Corynebacterium diphtheriae that affects the mucous membranes in the nose and throat, resulting in sore throat, fever, swollen glands (so much so that a “bull neck” is pathognomonic of this infection), and weakness
  • Croup: also called laryngotracheobronchitis; caused most commonly by a viral infection or, rarely, by a bacterial infection that results in swelling of the trachea and interferes with normal breathing
  • Gonorrhea: a sexually transmitted disease that affects both genders, manifesting on the genitals, rectum, and throat, commonly affecting teens (15–24 years) who engage in vaginal, anal, or oral sex
  • Pneumonia: an acute or chronic inflammation of lung tissue, which includes infection with bacteria, viruses, or fungi

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