A 22-year-old woman developed sudden hepatic encephalopathy and severe intestinal bleeding. She was diagnosed with acute fatty liver and hypersensitivity vasculitis and was successfully treated with whole plasma exchange, methylprednisolone pulse therapy, and transcatheter arterial embolization. Twenty-seven months later, she began complaining of lower abdominal fullness, tenderness, and nausea and vomiting. Histologic examination showed that she had developed gastrointestinal and renal amyloidosis with intestinal pseudoobstruction and proteinuria. The immunohistochemical study of the stomach, rectum, and kidney with anti-amyloid A fluorescent antibody showed that the systemic amyloid deposit was secondary to her underlying disease. This is the first report of amyloidosis occurring secondary to hypersensitivity vasculitis.