Croup Syndrome
Croup is the most common etiology for hoarseness, cough, and onset of acute stridor in febrile
children.
What is Croup Syndrome?
Croup is a common, primarily pediatric viral respiratory tract illness.
● Croup is the most common etiology for hoarseness, cough, and onset of acute
stridor in febrile children.
● As its alternative names, acute laryngotracheitis and acute
laryngotracheobronchitis, indicate, croup generally affects the larynx and trachea,
although this illness may also extend to the bronchi.
● This respiratory illness, recognized by physicians for centuries, derives its name from
an Anglo-Saxon word, kropan, or from an old Scottish word, roup, meaning to cry out
in a hoarse voice.
Pathophysiology
Viruses causing acute infectious croup are spread through either direct inhalation from a cough
and/or sneeze, or by contamination of hands from contact with fomites with subsequent touching
the mucosa of the eyes, nose, and/or mouth.
, ● The primary ports of viral entry are the nose and nasopharynx.
● The infection spreads and eventually involves the larynx and trachea.
● Inflammation and edema of the subglottic larynx and trachea, especially near the
cricoid cartilage, are most clinically significant.
● Histologically, the involved area is edematous, with cellular infiltration located in the
lamina propria, submucosa, and adventitia.
● This narrowing results in the seal-like barky cough, turbulent airflow, stridor, and
chest wall retractions.
● Decreased mobility of the vocal cords due to edema leads to the associated
hoarseness.
Statistics and Incidences
Croup is the most common pediatric illness that causes acute stridor, accounting for
approximately 15% of annual clinic and emergency department visits for pediatric respiratory
tract infections.
● Croup is primarily a disease of infants and toddlers, with an age peak incidence of
age 6 months to 36 months (3 years).
● In North America, incidence peaks in the second year of life, with an incidence of
about 5-6 cases per 100 toddlers.
● Although uncommon after age 6 years, croup may be diagnosed in the preteen and
adolescent years, and rarely in adults.
● The male-to-female ratio for croup is approximately 1.4:1.
● The disease occurs most often in late fall and early winter, but may present at any
time of the year.
● Approximately 5% of children will experience more than 1 episode.
Causes
Viruses causing acute infectious croup are spread through either direct inhalation from a cough
and/or sneeze, or by contamination of hands from contact with fomites with subsequent touching
the mucosa of the eyes, nose, and/or mouth.
● Parainfluenza viruses. Parainfluenza viruses (types 1, 2, 3) are responsible for
about 80% of croup cases, with parainfluenza types 1 and 2, accounting for nearly
66% of cases.
● Mycoplasma pneumoniae. The bacterial pathogen, Mycoplasma pneumoniae, has
also been identified in a few cases of croup.
Croup is the most common etiology for hoarseness, cough, and onset of acute stridor in febrile
children.
What is Croup Syndrome?
Croup is a common, primarily pediatric viral respiratory tract illness.
● Croup is the most common etiology for hoarseness, cough, and onset of acute
stridor in febrile children.
● As its alternative names, acute laryngotracheitis and acute
laryngotracheobronchitis, indicate, croup generally affects the larynx and trachea,
although this illness may also extend to the bronchi.
● This respiratory illness, recognized by physicians for centuries, derives its name from
an Anglo-Saxon word, kropan, or from an old Scottish word, roup, meaning to cry out
in a hoarse voice.
Pathophysiology
Viruses causing acute infectious croup are spread through either direct inhalation from a cough
and/or sneeze, or by contamination of hands from contact with fomites with subsequent touching
the mucosa of the eyes, nose, and/or mouth.
, ● The primary ports of viral entry are the nose and nasopharynx.
● The infection spreads and eventually involves the larynx and trachea.
● Inflammation and edema of the subglottic larynx and trachea, especially near the
cricoid cartilage, are most clinically significant.
● Histologically, the involved area is edematous, with cellular infiltration located in the
lamina propria, submucosa, and adventitia.
● This narrowing results in the seal-like barky cough, turbulent airflow, stridor, and
chest wall retractions.
● Decreased mobility of the vocal cords due to edema leads to the associated
hoarseness.
Statistics and Incidences
Croup is the most common pediatric illness that causes acute stridor, accounting for
approximately 15% of annual clinic and emergency department visits for pediatric respiratory
tract infections.
● Croup is primarily a disease of infants and toddlers, with an age peak incidence of
age 6 months to 36 months (3 years).
● In North America, incidence peaks in the second year of life, with an incidence of
about 5-6 cases per 100 toddlers.
● Although uncommon after age 6 years, croup may be diagnosed in the preteen and
adolescent years, and rarely in adults.
● The male-to-female ratio for croup is approximately 1.4:1.
● The disease occurs most often in late fall and early winter, but may present at any
time of the year.
● Approximately 5% of children will experience more than 1 episode.
Causes
Viruses causing acute infectious croup are spread through either direct inhalation from a cough
and/or sneeze, or by contamination of hands from contact with fomites with subsequent touching
the mucosa of the eyes, nose, and/or mouth.
● Parainfluenza viruses. Parainfluenza viruses (types 1, 2, 3) are responsible for
about 80% of croup cases, with parainfluenza types 1 and 2, accounting for nearly
66% of cases.
● Mycoplasma pneumoniae. The bacterial pathogen, Mycoplasma pneumoniae, has
also been identified in a few cases of croup.
