BACKGROUND: Langerhans cell histiocytosis ( LCH) with abnormal infiltratiation of Langerhans cells in various organs  is rare and leads to a heterogeneous  disease group . We aimed to present , the process of diagnosis and treatment of our patient with histiocytosis with multisystem involvement .

CASE  : When the 29 year old female patient admitted to our clinic who were asymptomatic, diagnosed four years ago at another center with central diabetes insipidus and hypogonadotropic hypogonadism than began  replacement therapy. In  hipofiz magnetic resonance imaging ( MRI) 3 mm lesion in the suprasellar region detected . During 2 -year follow-up  size of the lesion reached 13x11mm diameter and then referred to our clinic . Physical examination was normal except for obesity .  15x10 mm in size isointense   kontrast enhancement on T1 -and T2- weighted imaging of the hypothalamic lesion was detected   on pituitary MRI . Loss of signal hyperintensity of the neurohypophysis were also present . Because of visual field deterioration due to rapidly growing lesion    and  to obtain a tissue diagnosis  patient was operated by the decision of the of endocrinology - brain surgery council. Reactive fibrosis was evaluated as post-operative pathology , differential diagnosis couldn't be made. During follow-up, biopsies of catarrhal purulent material lesions that appear  in the left axilla and intergluteal   region revealed the  diagnoses of LCH . These findings , when combined with clinical course and radiological findings of hypothalamic involvement of the lesion was thought to be Langerhans cell  histiocytosis . During screening for other system involvement of LCH,  osteolytic lesion was also detected in the femur. LCH with multisystem involvement was diagnosed and systemic chemotherapy was started.