Thrombotic Thrombocytopenic Purpura is a particular form of thrombotic microangiopathy, characterized by petechial lesions, anemia, renal failure and fluctuating mental status. It is usually associated with an infection, drugs, or neoplasias. Confusing and rare, it is a real diagnostic challenge.

Harlequin syndrome corresponds to unilateral dysfunction of sympathetic system, characterized by flush and unilateral hyperhidrosis associated with hypo or anhidrosis and paleness of the opposite side. It is, usually, idiopathic. Rarely, it may be associated with compressive organic processes, iatrogenic causes and general diseases. It is a real therapeutic challenge.