A 32-year-old woman is evaluated for a painful rash occurring bilaterally on her lower extremities, which began 2 days ago. She was admitted to the hospital 5 days ago for diagnosis and treatment of pulmonary embolism with heparin and warfarin. Her father had a pulmonary embolism after a long airplane ride. Her medical history is otherwise unremarkable, and she takes no other medications.

On physical examination, vital signs are normal. She has non-blanchable macules and papules and areas of cutaneous necrosis in an angulated reticular pattern on the lower legs. The examination is otherwise unremarkable. Laboratory studies show a normal complete blood count, a normal peripheral blood smear, and an INR of 4.

Which of the following is the most likely diagnosis?

A. Factor V Leiden mutation
B. Plasminogen activator inhibitor 1 deficiency
C. Protein C deficiency
D. Prothrombin gene mutation

The most likely diagnosis for the patient is Protein C deficiency, a genetic disorder that affects the clotting ability of the blood and increases the risk of developing blood clots. Hence option C is correct.

Explanation:

The most likely diagnosis for the patient with a painful rash on her lower extremities is Protein C deficiency. Protein C deficiency is a genetic disorder that affects the clotting ability of the blood. Patients with this condition are at an increased risk of developing blood clots, which can lead to complications such as pulmonary embolism. In this case, the patient's history of pulmonary embolism, along with the presence of necrotic skin lesions and an elevated INR, are consistent with the diagnosis of Protein C deficiency.