Differential Diagnosis for High CRP with Chest Congestion and Normal WBC

Single Most Likely Diagnosis

• Viral Pneumonia: High CRP indicates inflammation, and chest congestion suggests a respiratory issue. A normal WBC count can be seen in viral infections, making viral pneumonia a likely diagnosis.

Other Likely Diagnoses

• Bacterial Pneumonia: Although the WBC count is normal, some cases of bacterial pneumonia, especially in the early stages or in partially treated cases, might not present with an elevated WBC count. The high CRP supports an infectious or inflammatory cause.
• Acute Bronchitis: This condition can cause chest congestion and may lead to an elevated CRP due to inflammation, even with a normal WBC count, especially if it's viral in nature.
• Pulmonary Embolism with Infarction: While not typically the first diagnosis that comes to mind with these symptoms, a pulmonary embolism can cause chest congestion and an elevated CRP due to infarction of lung tissue, without necessarily elevating the WBC count.

Do Not Miss Diagnoses

• Sepsis: Although the WBC count is normal, sepsis can present atypically, especially in the elderly or immunocompromised. High CRP and chest congestion could be indicative of a severe infection leading to sepsis.
• Pneumonia due to Atypical Organisms: Infections caused by organisms like Mycoplasma pneumoniae, Legionella pneumophila, or Chlamydophila pneumoniae can present with normal WBC counts but high CRP levels and significant chest symptoms.
• Cardiac Causes (e.g., Myocardial Infarction): High CRP is associated with inflammation and can be elevated in myocardial infarction. Chest congestion might be due to heart failure, making this a critical diagnosis not to miss.

Rare Diagnoses

• Eosinophilic Pneumonia: This rare condition can cause chest congestion and might present with a normal WBC count if the eosinophilia is not significant enough to elevate the total count, but CRP could be elevated due to inflammation.
• Lymphangitic Carcinomatosis: A rare condition where cancer spreads to the lymphatic vessels of the lungs, causing inflammation and potentially leading to high CRP and chest congestion without a significant elevation in WBC count.
• Sarcoidosis: Although more commonly associated with a chronic presentation, sarcoidosis can cause inflammation in the lungs, leading to chest congestion and elevated CRP, with a normal WBC count in some cases.