Differential Diagnosis for a Cough Worse in the Morning in a 6-Month-Old Infant

Single Most Likely Diagnosis

• Viral upper respiratory tract infection (URTI): This is the most common cause of cough in infants, and symptoms often worsen in the morning due to increased mucus production overnight.

Other Likely Diagnoses

• Allergic rhinitis: Allergies can cause chronic cough, which may be worse in the morning due to allergen exposure and increased mucus production.
• Gastroesophageal reflux disease (GERD): Stomach acid reflux can irritate the throat and cause a cough, which may worsen in the morning after lying down for an extended period.
• Environmental exposures: Exposure to tobacco smoke, pollution, or other irritants can cause a chronic cough, which may be worse in the morning.

Do Not Miss Diagnoses

• Pertussis (whooping cough): A highly contagious and potentially life-threatening illness, especially in young infants. Although less common, it's crucial to consider due to its severity.
• Foreign body aspiration: An infant may cough if an object is lodged in their airway, which requires immediate medical attention.
• Congenital heart disease: Certain heart defects can cause respiratory symptoms, including cough, due to pulmonary congestion.

Rare Diagnoses

• Cystic fibrosis: A genetic disorder that affects the respiratory and digestive systems, causing chronic cough and other symptoms.
• Primary ciliary dyskinesia: A rare genetic disorder that affects the movement of cilia in the respiratory tract, leading to chronic respiratory infections and cough.
• Tuberculosis: A bacterial infection that can cause cough and other respiratory symptoms, although it's relatively rare in infants in many parts of the world.