Differential Diagnosis for Viral Illness with Respiratory Symptoms

Single Most Likely Diagnosis

• Acute Sinusitis: The patient's symptoms of congestion, greenish-yellow mucus, postnasal drip, ear pressure, and sinus pressure following a viral illness are classic for acute sinusitis. The duration of 14 days also fits within the timeframe for the development of secondary bacterial sinusitis following a viral upper respiratory infection.

Other Likely Diagnoses

• Viral Upper Respiratory Infection (URTI) with Sinus Involvement: The initial viral illness could have directly involved the sinuses, leading to the described symptoms without a secondary bacterial infection.
• Allergic Rhinitis: If the patient has allergies, the symptoms could be due to an allergic reaction, especially if the greenish-yellow mucus is not purulent and the symptoms are seasonal or triggered by specific allergens.
• Influenza: Although the duration is a bit long for typical influenza, some cases can lead to prolonged symptoms, including sinus and ear pressure, especially if there are complications or co-infections.

Do Not Miss Diagnoses

• Streptococcal Pharyngitis: Although less likely given the primary symptoms are sinus and ear pressure, streptococcal pharyngitis can lead to significant complications if not treated, such as rheumatic fever or glomerulonephritis.
• Pneumonia: If the patient has a fever, cough, or shortness of breath in addition to the sinus symptoms, pneumonia should be considered, especially in vulnerable populations like the elderly or those with underlying health conditions.
• Meningitis: Although rare, if there are symptoms of severe headache, stiff neck, or altered mental status, meningitis must be considered and ruled out promptly due to its high morbidity and mortality.

Rare Diagnoses

• Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can cause sinusitis, but typically presents with more systemic symptoms and would be unusual without other findings like kidney involvement or rash.
• Tuberculous Sinusitis: Very rare in most populations, but should be considered in individuals with risk factors for tuberculosis, such as recent travel to or residence in endemic areas, immunocompromised states, or exposure to TB.
• Fungal Sinusitis: More common in immunocompromised patients, fungal sinusitis can present with similar symptoms but often has additional findings like facial pain, proptosis, or black nasal discharge.