This is the result of capillaritis, not a differential. It is the brownish "stain" left by red blood cells leaking from the capillaries.
This pigmentation follows a previous inflammatory process (like eczema) and lacks the characteristic "cayenne pepper" speckling of capillaritis.
While both occur on the lower legs, stasis dermatitis is driven by venous incompetence and is associated with edema, varicose veins, and more confluent brownish discoloration, not just fine petechiae.
Purpura from low platelets is often more widespread, can involve mucous membranes, and is associated with a low platelet count on a blood test, whereas capillaritis is a primary vessel wall issue.
Palpable purpura (raised, inflamed lesions) is the hallmark of small-vessel vasculitis, whereas the purpura of capillaritis is non-palpable and non-inflammatory.
