History and exam

Key diagnostic factors

common

symptoms increasing with agitation

Seen in all levels of severity.

distinctive seal-like barky cough

Key feature, required to make a diagnosis of croup.

age 6 months to 6 years

Occurs in this age group. Typically, it affects children between 6 months and 3 years of age, peaking in the second year of life.[1]

Croup can be seen in infants as young as 3 months of age, and may also occur, although rarely, in older children, adolescents, and adults.[1]

Other diagnostic factors

common

male sex

Male to female ratio: 1.4:1.[1]

peak season late autumn (North America)

Cases peak in late autumn in North America (September to December), which correlates with the peak prevalence of parainfluenza virus in the community.[3]

prodromal symptoms

Nonspecific upper respiratory tract symptoms (coryza, nonbarky cough, mild fever) for 12 to 48 hours may be present. Not a key feature in all cases; seal-like barky cough may present abruptly with no preceding illness.

abrupt onset of symptoms

Typical, but not essential to the diagnosis.

symptoms worse at night

Typical, but not essential to the diagnosis.

hoarse voice

Not essential to the diagnosis, but commonly seen.

uncommon

respiratory distress (sternal/intercostal indrawing, stridor)

In moderate/severe croup.

persistent agitation

In severe croup.

lethargy

In severe croup (more likely in impending respiratory failure).

asynchronous chest wall and abdominal movement

Impending respiratory failure.

fatigue

Impending respiratory failure.

signs of hypoxia (pallor or cyanosis)

Impending respiratory failure.

signs of hypercapnia (decreased level of consciousness secondary to rising PaCO₂)

Impending respiratory failure.

Risk factors

strong

age 6 months to 6 years

Occurs in this age group. Typically, it affects those between 6 months and 3 years of age, peaking in the second year of life.[1]

Croup can be seen in infants as young as 3 months of age, and may also occur, although rarely, in older children, adolescents, and adults.[1]

weak

male sex

Male to female ratio: 1.4:1.[1]

prior intubation

Small observational study indicates a weak link between a history of previous intubation and croup.[13]

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