Langerhans cell histiocytosis (LCH) is a clonal neoplasm that shows diverse clinical manifestations and courses of disease progression. The etiology and pathophysiology of LCH remain uncertain. We describe the clinical course of a 23-year-old Japanese woman with multi-system LCH, who showed rapid progression after steroid reduction and developed multi-organ failure. Liver biopsy showed LCH infiltration with fatty degeneration. She was treated with cytarabine, vincristine, and prednisolone according to the Japan LCH study group 02 protocol, without any clinical improvement. Low expression of Ki67 and bcl-2 failed to explain the rapid clinical course. Panhypopituitarism and hypothalamic dysfunction may have caused nonalcoholic fatty liver disease and liver failure. This case indicates that some multi-system LCH patients with hypopituitarism and hypothalamic dysfunction show very rapid progression and are difficult to treat.