Differential Diagnosis for Runny Nose, Cough, Sore Throat without Fever for 1 Week

Single Most Likely Diagnosis

• Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of symptoms like runny nose, cough, and sore throat without fever, especially when they have been present for a week. The lack of fever and the duration of symptoms suggest a viral etiology, which is often self-limiting.

Other Likely Diagnoses

• Allergic Rhinitis: This condition can cause chronic or recurrent runny nose, cough (due to postnasal drip), and sore throat. The absence of fever and the chronic nature of the symptoms could suggest an allergic cause.
• Sinusitis: While often associated with fever, sinusitis can present without fever, especially in its chronic form. The symptoms of runny nose, cough, and sore throat could be indicative of sinus inflammation.
• Acid Reflux (Gastroesophageal Reflux Disease, GERD): GERD can cause cough and sore throat due to the reflux of stomach contents into the esophagus, irritating the throat and respiratory tract.

Do Not Miss Diagnoses

• Pertussis (Whooping Cough): Although less common, pertussis can present with cough and runny nose, especially in individuals not vaccinated or with waning immunity. It's crucial to consider this diagnosis due to its potential for severe complications, especially in infants and young children.
• Influenza: Even though the patient does not have a fever, influenza can sometimes present without typical flu-like symptoms, especially in certain populations like the elderly or those with compromised immune systems.
• Tuberculosis (TB): A chronic cough can be a symptom of TB, and although less likely, it's a critical diagnosis not to miss due to its public health implications and the need for specific treatment.

Rare Diagnoses

• Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): This is a rare autoimmune disorder that can cause a variety of symptoms, including respiratory issues like cough and sore throat, but it would typically be accompanied by other systemic symptoms.
• Sarcoidosis: A condition that can affect multiple parts of the body, including the lungs, and cause symptoms like cough and sore throat, but it's relatively rare and usually presents with other findings like skin lesions or eye symptoms.

Workup and Treatment Plan

The initial approach should include a thorough history and physical examination. For the Single Most Likely Diagnosis and Other Likely Diagnoses, treatment is often supportive, focusing on symptom relief with over-the-counter medications for cough, runny nose, and sore throat. For allergic rhinitis, antihistamines or nasal corticosteroids may be prescribed. Sinusitis might require antibiotics if deemed bacterial. GERD is managed with lifestyle modifications and possibly proton pump inhibitors.

For Do Not Miss Diagnoses, specific tests are required: a PCR test for influenza, a pertussis test (PCR or serology) for whooping cough, and a tuberculin skin test or interferon-gamma release assay for TB. Treatment for these conditions is specific and requires prompt initiation.

For Rare Diagnoses, a more extensive diagnostic workup would be necessary, including blood tests, imaging studies (like chest X-rays or CT scans), and possibly biopsies, depending on the suspected condition. Treatment would depend on the specific diagnosis and could involve immunosuppressive medications.