· Morphology of early lesion: Minimal erythema with retiform purpura or with necrosis suggests occlusion with ischemic hemorrhage or infarction.
· Platelet plugs
o Heparin necrosis (distant or injection sites)
o Myeloproliferative thrombosis
o Paroxysmal nocturnal hemoglobinuria
o Thrombotic thrombocytopenic purpura (plugs mainly visceral vessels, skin lesions usually simple hemorrhage)
· Cold-related gelling or agglutination (lesions localize to acral, cold-exposed areas)
o Cryoglobulinemia, usually monoclonal
o Cryofibrinogenemia (often incidental finding in ill patients)
o Cold agglutinins (rarely occlusive, usually hemolytic)
· Embolization or crystal deposition (lesions localize to dependent or acral areas)
o Cholesterol emboli
o Oxalate crystal deposition
o Both usually have extensive livedo
o Hypereosinophilic syndrome
o Embolus from atrial myxoma, septic, or marantic endocarditis
o Crystal globulin vasculopathy
· Local or systemic changes in coagulation control
o Coumarin necrosis (altered protein C function)
o Disseminated intravascular coagulation with severe protein C deficiency or dysfunction
o Homozygous protein C or S deficiency
o Anti-phospholipid antibody/lupus coagulant
o Livedoid vasculitis atrophie blanche
· Occlusion caused by organisms growing in vessel and vessel walls (usually immunocompromised host)
o Vessel-invasive fungus (Mucor, Aspergillus, Cephalosporium, Rhizopus, etc.)
o Ecthyma gangrenosum (Pseudomonas)
o Disseminated strongyloidiasis
· Uncertain pathophysiology
o Cutaneous calciphylaxis
o Hemoglobinopathy occlusion (sickle cell, severe thalassemia): Probably sticky reticulocyte occlusion, sickling
o Lucio phenomenon in leprosy
o Degos disease—not purpuric
o Reperfusion necrosis
o Interferon injection
o Loxosceles spider bite
|