Differential Diagnosis for Fever with Normal Chest X-Ray (CXR) and Elevated C-Reactive Protein (CRP) and Neutrophils
Given the presentation of fever, normal CXR, CRP of 139.5, and neutrophils at 9.6, the differential diagnosis can be categorized as follows:
- Single Most Likely Diagnosis
- Bacterial infection (e.g., urinary tract infection, pneumonia not yet visible on CXR, or bacteremia): The elevated CRP and neutrophil count suggest a bacterial infection. Despite the normal CXR, pneumonia or another bacterial infection could be present, especially if the CXR was taken early in the course of the disease.
- Other Likely Diagnoses
- Viral infection: Although CRP is more commonly elevated in bacterial infections, some viral infections can also cause significant elevations in CRP and neutrophilia, especially if there is a secondary bacterial infection.
- Inflammatory conditions (e.g., appendicitis, cholecystitis): These conditions can cause fever, elevated CRP, and neutrophilia. The normal CXR does not rule out abdominal or pelvic pathology.
- Do Not Miss Diagnoses
- Sepsis: Regardless of the source, sepsis is a life-threatening condition that requires immediate recognition and treatment. The elevated CRP and neutrophils, along with fever, could indicate sepsis, especially if the patient shows signs of organ dysfunction.
- Neutropenic fever (if the patient is immunocompromised): Although the neutrophil count is elevated, in immunocompromised patients, even a normal or slightly elevated neutrophil count can represent a relative neutropenia, and fever in this context is a medical emergency.
- Rare Diagnoses
- Autoimmune disorders (e.g., rheumatoid arthritis, lupus): These can cause fever and elevated inflammatory markers but are less likely given the acute presentation and the specific combination of lab results.
- Malignancy: Certain malignancies can cause fever and elevated CRP, but this would be less common and might be associated with other symptoms or findings not mentioned here.
Each of these diagnoses should be considered in the context of the patient's full clinical presentation, including history, physical examination, and additional diagnostic tests as needed.