Diagnosis: Bronchiolitis
The diagnosis is B. Bronchiolitis. This 2-month-old infant presents with the classic clinical picture of viral bronchiolitis: viral upper respiratory prodrome (cough, runny nose) followed by lower respiratory tract involvement with expiratory wheeze, increased work of breathing, and nasal flaring 1.
Why Bronchiolitis is the Correct Diagnosis
The American Academy of Pediatrics defines bronchiolitis as a constellation of clinical signs and symptoms in children younger than 2 years, including a viral upper respiratory prodrome followed by increased respiratory effort and wheezing 2. This patient's presentation matches this definition precisely:
- Age under 12 weeks places this infant in the highest risk category for bronchiolitis 1
- Viral prodrome with rhinorrhea and cough preceding lower respiratory symptoms 2, 1
- Expiratory wheeze in all lower lung zones indicates diffuse bilateral lower airway involvement characteristic of bronchiolitis 1
- Increased work of breathing with nasal flaring reflects the acute inflammation and bronchiolar obstruction from epithelial destruction, inflammatory infiltration, and mucus accumulation 3
- Absence of fever does not exclude bronchiolitis, as fever is not a necessary diagnostic criterion 1
Why the Other Options Are Incorrect
Pneumonia (Option A)
- Pneumonia typically presents with focal findings on examination rather than diffuse bilateral wheezing 1
- This infant has diffuse expiratory wheeze in all lower lung zones, not focal consolidation
Bronchial Asthma (Option C)
- The American Academy of Pediatrics states that children with recurrent wheezing episodes after the first year of life likely have asthma, but a first episode in an infant under 2 years with viral prodrome is more likely bronchiolitis 1
- This is a 2-month-old with a first presentation following viral symptoms, making bronchiolitis the appropriate diagnosis
Viral Croup (Option D)
- Viral croup presents with inspiratory stridor, barky cough, and upper airway obstruction, unlike bronchiolitis which presents with expiratory wheezing and lower airway disease 1
- This infant has expiratory wheeze (lower airway) not inspiratory stridor (upper airway)
Clinical Management Considerations
The diagnosis should be made clinically based on history and physical examination alone, without routine chest x-rays or laboratory studies 2, 1.
Risk Assessment for This Patient
- Age under 12 weeks is a significant risk factor for severe disease requiring careful monitoring 2, 1
- Assess for additional risk factors including prematurity, cardiopulmonary disease, or immunodeficiency 2, 1