To find out the most appropriate management,clinical features of 18 cases of adult multisystem langerhans cell histiocytosis(LCH)have been analyzed.The patients comprising of 9 males and 9 females were median age of 36 years,ranging from 18-53 years at diagnosis.Regarding the initial symptoms,7 patients(2 males and 5 females)showed central diabetes insipidus(CDI)and other endocrine symptoms with thickened pituitary stalk or a mass at the hypothalamic region.Additional 2 patients initiated the disease with CDI with no immediate diagnosis.In the remaining patients,the disease begun with single(n=3)or multiple(n=1)spinal bone lesion(s)in 4 patients(all males),with multiple bone lesions in 3 patients(1 male and 2 females),with single skull lesion in one female patient and with ambiguous symptoms including hypothyroidism in the remaining one male patient.We also recognized the correlation between pregnancy/childbirth and LCH in 4 patients.In terms of treatment,9 patients received systemic immuno-chemotherapy alone,of which the majority received vinblastine-based chemotherapy while 4 received 2-chlorodeoxyadenosine.Five had a combination of immuno-chemotherapy with surgical resection or radiotherapy,2 had immunotherapy alone,2 had surgical resection followed by observation alone to date.Three patients received hematopoietic stem cell transplantation after extensive chemotherapy.In terms of outcome,15 patients are alive(9 with active disease,6 without active disease),with a median of 66 mo(range 17-166 mo),two died of disease while the remaining 1 lost to follow-up.Based on these results,we think that early diagnosis and rapid introduction of appropriate treatment are essential,in order to overcome the problems relevant to adult LCH.