This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in


Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Croup is a generic term that covers a heterogeneous group of diseases that affects the larynx, trachea, and bronchi (1):

  • components of the croup syndrome include (1)
    • laryngotracheitis
    • laryngotracheobronchitis
    • laryngotracheobronchopneumonitis
    • spasmodic croup
  • some define croup as two types
    • infectious croup:
      • commonly caused by virus
        • viral croup
      • rarely caused by bacterium
        • Mycoplasma pneumoniae is a rare cause of mild croup in children (1)
        • rarely caused by Staphylococcus aureus
    • spasmodic croup

  • viral croup (1)
    • is an upper respiratory tract infection (acute laryngotracheobronchitis)
    • affects children 6 months to 12 years of age
    • has a peak incidence at two years of age
    • is the commonnest cause of airway obstruction in children 6 months to 6 years of age (1)
    • boys are affected more often than girls
    • is commonly seen in the fall and winter months
    • parainfluenza viruses (type1, 2, 3) account for the majority of cases
      • most common cause is Human parainfluenza virus 1 (HPIV-1)
      • rarely, other viruses are responsible, for example
        • influenza A and B viruses
        • adenovirus
        • measles
        • RSV (Respiratory syncytial virus)
    • the onset is slower and is usually preceded by a coryzal prodrome (with fever) (1)

  • spasmodic croup (1)
    • associated with the viruses that cause viral croup
    • onset is sudden, without a viral prodrome
    • histology of the subglottic tissues shows noninflammatory oedema
    • tends to recur
    • may represent an allergic reaction to viral antigens
  • often the distinction of the two types is impossible
    • hence sometimes spasmodic croup is considered part of the spectrum of viral croup(1)


Create an account to add page annotations

Add information to this page that would be handy to have on hand during a consultation, such as a web address or phone number. This information will always be displayed when you visit this page