The rash that becomes purpuric, petechial, hemorrhagic, or ecchymotic.

Hemorrhagic rashes are observed in a wide variety of conditions, ranging from harmless to life-threatening. This review offers a stepwise approach, which helps limit the possible differential diagnoses based on the clinical manifestations and the clinical picture. The most common and most important conditions, including infectious, coagulation and embolic disorders, vasculitides, and vasculopathies, are briefly reviewed focusing on morphology. Dermatologists often need to distinguish among infectious, reactive, or autoimmune etiologies of the rash and determine if the condition is dangerous or even life-threatening in order to make the right decision. Dermatologic expertise provides vital input in the diagnosis and care of complex interdisciplinary patients, such as those with sepsis, purpura fulminans, and thrombotic thrombocytopenic purpura.