Differential Diagnosis for Acute Right Lower Extremity DVT

Given the patient's significant thrombotic history, including a factor five Leiden mutation, recent DVT in the left lower extremity, and a history of pulmonary embolism, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Post-thrombotic syndrome: This condition occurs as a complication of DVT and can cause symptoms similar to DVT, such as swelling, pain, and discoloration of the affected limb, even in the absence of a new clot. The patient's recent history of DVT and the negative ultrasound for a new clot make this a plausible explanation for her symptoms.

• Other Likely Diagnoses

  • Recurrent DVT: Despite the negative ultrasound, the possibility of a recurrent DVT, especially in a patient with a high-risk profile (factor five Leiden mutation and recent DVT), cannot be entirely ruled out without further investigation, such as a CT scan or repeat ultrasound.
  • Musculoskeletal injury or strain: Given the patient's recent history of DVT and possible decreased mobility, a musculoskeletal injury could mimic the symptoms of DVT.
  • Cellulitis: An infection of the skin and subcutaneous tissues, which could present with similar symptoms to DVT, such as swelling, redness, and warmth of the affected limb.

• Do Not Miss Diagnoses

  • Pulmonary embolism: Although the concern is for DVT, given the patient's history of pulmonary embolism, it is crucial not to miss another potential PE, which could present with symptoms such as shortness of breath, chest pain, or even leg symptoms if related to a large clot burden.
  • Phlegmasia cerulea dolens: A severe form of DVT characterized by significant swelling, pain, and cyanosis of the affected limb, which can lead to limb ischemia and requires immediate intervention.

• Rare Diagnoses

  • May-Thurner syndrome: A rare condition where compression of the left common iliac vein can lead to DVT. Although less likely given the presentation in the right lower extremity, it's a consideration in patients with recurrent or unexplained DVTs.
  • Cancer-associated thrombosis: Certain cancers can increase the risk of thrombosis. Given the patient's significant thrombotic history, an underlying malignancy, although rare, should be considered and ruled out with appropriate screening.