Differentials
Bacterial pneumonia
SIGNS / SYMPTOMS
Bacterial pneumonia is much less common in this age group than bronchiolitis.
Infants with pneumonia generally have higher fever (≥40°C) than with bronchiolitis.
Wheezing is not a common finding in pneumonia.
INVESTIGATIONS
An FBC may demonstrate leukocytosis and neutrophilia.
The presence of a focal infiltrate on chest x-ray would increase the suspicion of bacterial pneumonia.
Chlamydial pneumonia
SIGNS / SYMPTOMS
The mother may have a history of vaginal chlamydial infection.
Up to half of infants with chlamydial pneumonia have a history of neonatal conjunctivitis.
The clinical course is usually subacute and not associated with upper respiratory tract infection.
Patients are usually afebrile. The cough may have a distinctive staccato-like quality. Crackles are more common than wheezes in chlamydial pneumonia.
INVESTIGATIONS
Eosinophilia is a feature of chlamydial pneumonia that is not seen in bronchiolitis.
Diagnosis can be made by culture or antigen detection from nasopharyngeal secretions.
Cystic fibrosis (CF)
SIGNS / SYMPTOMS
CF is usually associated with symptoms and signs of pancreatic insufficiency, such as steatorrhoea, failure to thrive, and fat-soluble-vitamin deficiencies.
A family history of CF may be present in affected infants.
CF lung disease usually presents as chronic cough.
It is insidious in onset and not associated with upper respiratory tract symptoms.
INVESTIGATIONS
Measurement of sweat chloride by quantitative pilocarpine iontophoresis will be elevated (>60 mmol/L) in almost all infants with CF.
Laryngotracheobronchitis (croup)
SIGNS / SYMPTOMS
A viral infection of the upper airways, often caused by parainfluenza viruses.
Characterised by fever, inspiratory stridor, hoarse cry, and a barking cough.
Symptoms often worsen at night.
INVESTIGATIONS
Diagnosis is usually clinical.
Sub-glottic narrowing may be seen on an anteroposterior (AP) neck radiograph; however, this investigation is rarely indicated.
Asthma
SIGNS / SYMPTOMS
Infants with recurrent episodes of wheezing often have atopic dermatitis, a history of food allergies, peripheral eosinophilia, and a parent with asthma. Whether a first episode of wheezing represents bronchiolitis or eventual asthma cannot always be distinguished.
INVESTIGATIONS
Eosinophilia on an FBC is more consistent with asthma.
The diagnosis is usually clinical, based on historical features of atopy, and response to bronchodilator therapy.
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