Differential Diagnosis for Asymptomatic Fever and Elevated D-Dimer

Given the presentation of an asymptomatic patient with fever for 3 days and a significantly elevated D-Dimer level of 7000 without any abnormalities on CT chest, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Viral Infection: Many viral infections can cause fever and elevated D-Dimer levels without specific findings on CT chest. The absence of symptoms other than fever and the lack of abnormalities on imaging make this a plausible explanation. Viral infections such as COVID-19, influenza, or other respiratory viruses could be considered, especially in the context of current or recent outbreaks.

• Other Likely Diagnoses

  • Deep Vein Thrombosis (DVT): Although the CT chest is normal, DVT can cause elevated D-Dimer levels. The absence of symptoms does not rule out DVT, as many are asymptomatic. Ultrasound of the legs would be necessary to evaluate for this condition.
  • Pulmonary Embolism (PE) with a Normal CT Chest: While the CT chest is reported as normal, small or peripheral PEs might not be visible. Given the significantly elevated D-Dimer, further evaluation with a ventilation-perfusion scan or a repeat CT with thinner slices might be warranted.
  • Inflammatory Conditions: Conditions like rheumatoid arthritis, lupus, or other autoimmune diseases can cause fever and elevated D-Dimer levels due to inflammation.

• Do Not Miss Diagnoses

  • Septic Thrombophlebitis: This condition involves infection of the venous thrombi and can be life-threatening. It might present with fever and elevated D-Dimer without specific findings on CT chest.
  • Ovarian Vein Thrombosis: Particularly in postpartum women or those with pelvic infections, ovarian vein thrombosis can cause fever and elevated D-Dimer levels.
  • Neoplasm: Certain cancers can cause elevated D-Dimer levels due to associated thrombosis or tumor-related coagulopathy. Although less likely, this is a critical diagnosis not to miss.

• Rare Diagnoses

  • Thyroid Storm: Although rare, thyroid storm can cause fever, tachycardia, and elevated D-Dimer levels due to the hypercoagulable state associated with severe thyrotoxicosis.
  • Heparin-Induced Thrombocytopenia (HIT): If the patient has been exposed to heparin recently, HIT could be a rare but serious cause of elevated D-Dimer levels and thrombosis.
  • Antiphospholipid Syndrome: This autoimmune disorder can cause thrombosis and elevated D-Dimer levels. It is less common but should be considered in the appropriate clinical context.

Each of these diagnoses requires careful consideration of the patient's full clinical picture, including medical history, physical examination, and additional diagnostic testing as indicated.