By the study of 4 personal cases and a review of the literature, the authors describe the symptoms which may complicate and even reveal an essential thrombocythemia. They are: painful symptoms which indicate a permanent or paroxystic vasculomotor syndrome by their localization and their course: -erythematous lesions of an inflammatory livedo type located on the legs and blue-red reticular spots on the sole of the foot: --occurrence of gangrene on finger ends or of necrotic ulcerations of the legs. Etiological conditions, exploration of primary hemostasis, physiopathology of the troubles are described. As for therapeutics the antiaggregants have a suspensive effect on the symptoms but only the control of the hematological status may allow recovery.