Differential Diagnosis for Patient with Viral Symptoms and Intermittent Blood-Tinged Sputum

Single Most Likely Diagnosis

• Influenza with secondary bacterial pneumonia: This is a common cause of viral symptoms, and the presence of blood-tinged sputum could indicate a secondary bacterial infection.

Other Likely Diagnoses

• Acute bronchitis: This condition often presents with cough and sputum production, and blood-tinged sputum can occur, especially if there is a secondary infection.
• Pneumonia (viral or bacterial): Pneumonia can cause viral symptoms and blood-tinged sputum, especially if there is an infection with a pathogen such as Streptococcus pneumoniae or Haemophilus influenzae.
• Asthma exacerbation: Asthma can cause cough and sputum production, and blood-tinged sputum can occur if there is airway inflammation or infection.

Do Not Miss Diagnoses

• Pulmonary embolism: Although less likely, pulmonary embolism can cause sudden onset of symptoms, including cough and blood-tinged sputum, and is a potentially life-threatening condition.
• Tuberculosis: TB can cause chronic cough and sputum production, including blood-tinged sputum, and is an important diagnosis to consider, especially in high-risk populations.
• Lung cancer: Lung cancer can cause cough and sputum production, including blood-tinged sputum, and is an important diagnosis to consider, especially in patients with a history of smoking.

Rare Diagnoses

• Goodpasture's syndrome: This is a rare autoimmune disease that can cause pulmonary hemorrhage and renal failure, and is an important diagnosis to consider in patients with unexplained blood-tinged sputum.
• Wegener's granulomatosis: This is a rare autoimmune disease that can cause pulmonary and renal inflammation, and is an important diagnosis to consider in patients with unexplained blood-tinged sputum.

Diagnostic Studies

To evaluate the patient's condition, the following diagnostic studies would be ordered:

• Chest X-ray or CT scan to evaluate for pneumonia, pulmonary embolism, or other lung abnormalities
• Complete blood count (CBC) to evaluate for signs of infection or inflammation
• Blood cultures to evaluate for bacterial infection
• Sputum Gram stain and culture to evaluate for bacterial infection
• Influenza testing (e.g. rapid antigen test or PCR) to evaluate for influenza infection
• Pulmonary function tests (e.g. spirometry) to evaluate for asthma or other lung diseases
• Urine analysis to evaluate for signs of renal disease (e.g. TB or Goodpasture's syndrome)