Rocky Mountain spotted fever presenting as thrombotic thrombocytopenic purpura.

A patient presented with findings compatible with thrombotic thrombocytopenic purpura. The diagnosis of Rocky Mountain spotted fever was also considered because the patient was a hunter in a tick-infested area. He was treated for both diagnoses. The patient recovered and a diagnosis of Rocky Mountain spotted fever was confirmed by serologic methods. Clinical symptoms and hematologic parameters of severe Rocky Mountain spotted fever may resemble thrombotic thrombocytopenic purpura, implying that there may be similarities in the pathophysiology of both disorders.