Langerhans' cell histiocytosis represents a diverse group of rare disorders characterized by proliferation and infiltration of various organs by bone marrow-derived abnormal Langerhans' cells. These diorders exhibit varied patterns of organ involvement, age distribution, prognosis and clinical manifestation. Here in we discuss an adult presentation of the disease in a 43 years old lady and summarize the latest recommendations regarding the classification, pathogenesis, work up and treatment of adult patients with these disorders.