title: Histiocytosis X: Characteristics, behavior, and treatments as illustrated in a case series.
abstract: BACKGROUND
  Langerhans cell histiocytosis (LCH) is a proliferative disorder predominantly found in children. It often presents with pain in calvarium or spine and may cause neuroendocrine symptoms. The gold standard for diagnosing LCH is the detection of Birbeck Granules by EM. Here, we describe two unique presentations of LCH and we review current treatment guidelines.
  
  
  METHODS
  The first patient was a 23-year-old man who presented with progressive swelling and redness of the left eye. MRI revealed a left retrobulbar lesion extending into the middle cranial fossa with no signal abnormality in the brain parenchyma. The lesion was resected and pathological analysis revealed LCH. Bone scans were negative and the patient was discharged soon after. He later underwent fractionated radiotherapy (cumulative dose 26 Gy). Follow-up MRIs show no disease at 24 months post-op. The second patient was a 56-year-old man with left frontal skull pain for 5 months. Imaging showed a solitary osteolytic lesion extending into both dura and scalp with no signal abnormality of the parenchyma. Excisional biopsy revealed LCH. Surgery was well tolerated and follow-up imaging shows no recurrence at 24 months post-op.
  
  
  CONCLUSIONS
  We demonstrate that LCH, though uncommon, must remain on the differential when osteolytic lesions present in the adult. Although LCH often has the clinical and radiographical presentation of an abscess, pathology analysis can successfully diagnose LCH based on markers and morphological characteristics. LCH has an excellent prognosis when treated aggressively with surgical resection and radiotherapy as both of our patients were and are now disease free at 2 year follow-up.
authors.affiliation: Department of Neurosurgery, Beth Israel Deaconess Medical Center, One Deaconess Road, Boston, MA, USA.
authors.forename: Ekkehard M
authors.initials: EM
authors.lastname: Kasper
authors.forename: David H
authors.initials: DH
authors.lastname: Aguirre-Padilla
authors.forename: Raanan Y
authors.initials: RY
authors.lastname: Alter
authors.forename: Matthew
authors.initials: M
authors.lastname: Anderson