Essential thrombocythemia presenting as localized livedo reticularis.

Essential thrombocythemia is a chronic myeloproliferative disorder characterized by a persistent and absolute increase in the peripheral platelet count (>600,000/mm) in the absence of another underlying disorder. From a clinical point of view, it is characterized by thrombotic manifestations that primarily involve the central nervous system as strokes and transient ischemic attacks and also affects other systems, causing gastrointestinal hemorrhages and arterial or venous thrombosis. Cutaneous manifestations may complicate essential thrombocythemia, but they may be a helpful guide to the diagnosis. These manifestations appear up to 22% of patients and may even be the presenting sign of the disease in up to 10% of them. We present a case of a previously healthy woman who was diagnosed with essential thrombocythemia after the onset of localized livedo reticularis. The case was immunohistochemically studied, supporting the role of the increased platelet number in the pathogenesis of the livedo reticularis lesions.