A 24-year-old male presented with severe pain and bluish discoloration of the right arm for 2 days, which he had noticed shortly after receiving an intramuscular injection of triamcinolone for recurrent episodes of urticaria, in the right deltoid region.

On examination, there was a livedoid pattern of non-blanchable, violaceous discoloration extending from the deltoid area to the distal third of the forearm with associated induration. The local area was warm and tender to the touch. There was no regional lymphadenopathy, and no other relevant findings.

The patients platelet count, bleeding and clotting times, prothrombin time, and international normalized ratio (INR) were unremarkable. There was no previous history of any bleeding disorder. The patient denied any intake of drugs, such as aspirin and warfarin.

What other investigations would you propose for this patient? What is the differential diagnosis?