Differential Diagnosis for a 73-year-old with Sudden Onset of Symptoms

Given the symptoms of swelling of the lymph nodes of the neck, congestion, runny nose, and sore throat in a 73-year-old, with a negative at-home COVID test, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Viral Pharyngitis: This is the most likely diagnosis given the symptoms of sore throat, runny nose, and congestion, which are typical of a viral upper respiratory infection. The negative COVID test reduces the likelihood of COVID-19, but does not rule out other viral causes.

• Other Likely Diagnoses

  • Bacterial Pharyngitis: Although less common than viral pharyngitis, bacterial causes such as Streptococcus pyogenes (Group A strep) need to be considered, especially if the sore throat is severe or accompanied by fever and swollen lymph nodes.
  • Influenza: Despite the negative COVID test, influenza can present with similar symptoms and should be considered, especially during flu season.
  • Mononucleosis: Caused by Epstein-Barr virus, this condition can present with sore throat, fever, and lymphadenopathy, although it's more common in younger populations.

• Do Not Miss Diagnoses

  • Lymphoma: Although rare, lymphoma can present with lymphadenopathy and should be considered, especially in an older adult with persistent or severe symptoms.
  • Tuberculosis (TB): TB can cause lymphadenopathy and respiratory symptoms, and although less common, it's a critical diagnosis not to miss due to its public health implications and the need for specific treatment.
  • HIV: Acute HIV infection can present with flu-like symptoms, including sore throat and lymphadenopathy. Given the potential for severe consequences if untreated, HIV should be considered in the differential diagnosis.

• Rare Diagnoses

  • Toxoplasmosis: This parasitic infection can cause lymphadenopathy but is less common and typically associated with specific risk factors such as immunocompromised states or exposure to undercooked meat.
  • Cytomegalovirus (CMV) Infection: CMV can cause a mononucleosis-like syndrome with lymphadenopathy, particularly in immunocompromised individuals or those with specific risk factors.
  • Syphilis: Secondary syphilis can present with lymphadenopathy and a variety of other symptoms, but it is relatively rare and usually associated with a characteristic rash and sexual exposure history.

Next Steps

Given these considerations, the next steps would include:

• A thorough physical examination to assess the extent of lymphadenopathy and other signs of infection.
• Laboratory tests such as a complete blood count (CBC), blood cultures, and possibly a mononucleosis spot test or rapid strep test depending on the clinical presentation.
• Consideration of further testing for influenza, HIV, TB, or other specific pathogens based on risk factors and clinical judgment.
• Empiric antibiotic treatment may be considered if bacterial pharyngitis is suspected, but this should be guided by culture results when possible to ensure appropriate use of antibiotics.