Pathology

Pathology/C/28

Lesions of the upper respiratory tract

上気道の病変

タグ
High-yield / ポイント

Upper Respiratory Tract Infections

Common Cold

  • Most frequent acute URTI
  • Clinical features: nasal congestion + watery discharge, sneezing, dry sore throat, slight fever
  • Common pathogens: rhinovirus, coronavirus, RSV, parainfluenza/influenza, adenovirus, enterovirus, Group A β-hemolytic streptococci
  • Occur in fall/winter; self-limiting (~1 week)

Rhinitis (inflammation of nasal mucosa)

  1. Allergic rhinitis (hay fever)
    • Triggered by plant pollens, fungi, dust mites, animal allergens
    • IgE-mediated hypersensitivity type I: allergen → B-cell activation → IgE → mast cell binding → re-exposure → histamine release → itching, swelling, mucus production
  2. Infectious rhinitis (common cold)
    • Agents: rhinovirus, adenovirus, echovirus
    • Symptoms: catarrhal discharge (mucus buildup)
  3. Chronic rhinitis
    • Sequel to acute rhinitis + secondary bacterial infection
    • Associated with deviated septum or nasal polyps (non-neoplastic allergic reaction; histology: edematous mucosa + eosinophilic infiltrate)

Tonsillitis

  • Inflammation of tonsils; reactive lymphoid hyperplasia → enlarged, reddened tonsils with dotted exudate from tonsillar crypts (follicular tonsillitis)
  • Symptoms: sore throat and fever
  • Causes: common cold viruses, Streptococcus pyogenes
  • Streptococcal tonsillitis: must treat early to prevent poststreptococcal glomerulonephritis, acute rheumatic fever, abscesses

Sinusitis

  • Acute: preceded by acute/chronic rhinitis; sinuses inflamed and swollen
  • Chronic: recurring or prolonged acute sinusitis → especially without drainage; mixed microflora

Acute Pharyngitis

  • Inflammation of the pharynx; sore throat + pharyngeal inflammation
  • Caused by common cold viruses
  • More severe with tonsillitis: S. aureus
  • Pharyngeal vesicles and ulcers (herpangina) → coxsackievirus A
  • Kissing disease → EBV → mononucleosis infectiosa

Otitis Media

  • Inflammation of the middle ear; due to Eustachian tube dysfunction (from nasopharyngeal inflammation)
  • Common in young children
  • Acute otitis media: abrupt ear pain; Eustachian tube blockage → air buildup; agents: S. pneumoniae, H. influenzae, Moraxella catarrhalis
  • Otitis media with effusion: usually asymptomatic; fluid collection in middle ear

Laryngitis

  • Inflammation of the larynx → hoarse voice or loss of vocal function (vocal cord irritation)
  • Acute: from irritants, allergic reactions, voice overuse, or common cold agents; acute = few days, chronic = >3 weeks
    • Tuberculous laryngitis: TB infection → coughing up infected sputum
    • Diphtheritic laryngitis: Corynebacterium diphtheriae → exotoxin → mucosal necrosis + fibrinopurulent exudate → pseudomembrane formation → aspiration → airway obstruction
  • Acute bacterial epiglottitis: H. influenzae; younger children; painful airway obstruction with abrupt onset
  • Laryngotracheobronchitis: parainfluenza virus; children; inspiratory stridor + harsh persistent cough; may lead to respiratory failure

Tracheitis

  • Inflammation of the trachea; most common cause: S. aureus (often follows viral URTI)
  • Most serious in young children (small trachea easily blocked by swelling)
  • Symptoms: inspiratory stridor (high-pitched wheezing), coughing, chest pain, fever

💡 High-yield: Allergic rhinitis = IgE/type I hypersensitivity. Streptococcal tonsillitis → glomerulonephritis + rheumatic fever. Pharyngitis: herpangina = coxsackievirus A; EBV = mononucleosis. Epiglottitis = H. influenzae; children. Diphtheria = C. diphtheriae; pseudomembrane → airway obstruction.