Condition	Characteristics
Cold urticaria	Pruritic, erythematous, nonpetechial wheals with central pallor that are induced by exposure to cold temperature; positive cold-stimulation test result if wheal develops after skin has been rewarmed
Essential mixed cryoglobulinemia	Cryoglobulin deposition in small- to medium-size blood vessels causing vasculitis, petechiae, and palpable purpura
Henoch-Schönlein purpura	Immunoglobulin A–mediated systemic vasculitis causing a purpuric rash on the extremities; typically associated with arthralgias and abdominal pain; usually affects children
Idiopathic thrombocytopenic purpura	Autoimmune destruction of platelets causing a petechial, nonblanching rash; may present with easy bruising or bleeding
Schamberg's disease	Hemosiderin deposition from leakage of surface blood vessels; orange-brown, speckled discoloration; typically affects lower limbs