Langerhans cell histiocytosis of pituitary stalk.

A four-year-old male child presented with increased Typically the lesions are round or oval-shaped with wellurine output and excessive thirst for eight months. On defined margins and bevelled edge. Individual lesions examination he had multiple scalp swellings with mild may coalesce giving a geographic appearance to the skull hepatosplenomegaly. Urine specific gravity was decreased suggestive of diabetes insipidus. Skull radiograph revealed multiple well-defined geographic lytic lesions in the calvarium with bevelled margins [Figure 1]. On MR examination of sella, the posterior pituitary bright spot was not seen on T1W image [Figure 2]. The pituitary stalk was thickened and showed uniform enhancement [Figure 3]. The characteristic radiographic feature of skull lesions, MRI findings and hepatosplenomegaly strongly suggested the possibility of Langerhans cell histiocytosis (LCH) which was confirmed on bone marrow biopsy. LCH is a wide-spectrum disease characterized by proliferation of abnormal histiocytes. It encompasses three classical clinical syndromes which in increasing order of severity are: eosinophilic granuloma (solitary bone lesion), Hand-Schuller-Christian disease (skull lesion, exophthalmos and diabetes insipidus) and Figure 2: T1W sagittal image. The bright spot of the posterior Letterer-Siwe disease (multisystemic rapidly progressive pituitary is not seen and the pituitary stalk is thickened. Isointense form). The skull bones are most commonly involved. soft tissue mass is seen in the clivus and sphenoid bone