Differential Diagnosis for a 9-Month-Old with Cough Mostly at Night and No Fever
- Single Most Likely Diagnosis
- Viral Upper Respiratory Infection (URTI): This is the most common cause of cough in infants, especially when it worsens at night. The absence of fever does not rule out a viral infection, as many viral URIs can present without fever, especially in younger children.
- Other Likely Diagnoses
- Allergic Rhinitis: Allergies can cause cough, especially at night, due to postnasal drip. In infants, this might be due to allergies to dust mites, pet dander, or other environmental allergens.
- Gastroesophageal Reflux Disease (GERD): GERD can cause coughing, particularly when the infant is lying down, as stomach acid can flow up into the esophagus and irritate the throat.
- Asthma: Although less common in infants, asthma can present with cough as a predominant symptom, often worsening at night.
- Do Not Miss Diagnoses
- Pertussis (Whooping Cough): Although vaccination has reduced its incidence, pertussis can still occur, especially in areas with low vaccination rates or in infants too young to be fully vaccinated. The cough can be severe and is often worse at night.
- Foreign Body Aspiration: This is a medical emergency that can present with sudden onset of cough, especially if the object is lodged in the airway. It's crucial to consider this diagnosis, even if the history does not clearly suggest aspiration.
- Congenital Heart Disease: Severe, uncorrected congenital heart defects can lead to heart failure, which may present with cough among other symptoms. While less likely, it's critical not to miss this diagnosis.
- Rare Diagnoses
- Cystic Fibrosis: This genetic disorder can lead to recurrent respiratory infections and chronic cough. It's less likely but should be considered in infants with persistent or severe respiratory symptoms.
- Primary Ciliary Dyskinesia (Kartagener Syndrome): A rare genetic disorder affecting the cilia, leading to chronic respiratory infections and cough.
- Tuberculosis: Although rare in many parts of the world, TB can cause chronic cough and is a critical diagnosis not to miss, especially in areas with high prevalence or in children exposed to individuals with TB.