title: Pulmonary Langerhans cell histiocytosis: a variable disease in childhood.
abstract: BACKGROUND
  Pulmonary Langerhans cell histiocytosis (PLCH) is rare in childhood but occurs most commonly in children with multisystem (MS) LCH. In adults, by contrast, the lung is the most common and usually the sole organ affected. This retrospective study describes the clinical manifestation, course, and outcome of PLCH in children consecutively diagnosed at two Canadian institutions.
  
  
  METHODS
  The medical records of children (<18 years of age) consecutively diagnosed with LCH at the two institutions, were examined to ascertain the demographic details, pathological diagnosis, and organs involved. Further clinical details including, the clinical manifestation, details of therapy, course of lung disease, and clinical outcome were extracted for patients with PLCH. Initial and follow-up lung radiographs and CT scans were re-reviewed.
  
  
  RESULTS
  Of the 178 patients with LCH, 40 (22.5%) presented with MS disease. Thirteen (7.3%) had PLCH, seven at initial diagnosis, and six at the time of disease progression. The median age was 10.1 months and mean was 11.9 months at diagnosis of PLCH. Lung involvement was always in the context of MS LCH, and half of the patients had no respiratory symptoms. Disease-free survival was around 70%, with a mean follow-up duration of 7 years. Of the four patients who died, three had other risk-organ involvement. Five of the nine surviving patients have had complete radiological resolution of PLCH.
  
  
  CONCLUSIONS
  PLCH is seen in less than 10% of childhood LCH, but more than 30% of MS LCH. About half of children with PLCH may be asymptomatic, and the prognosis appears to depend on the presence or absence of other risk-organ involvement. The MS PLCH found in children appears to be a different disease from the single system (SS) PLCH seen in adults.
authors.affiliation: Department of Pediatrics, Division of Hematology/Oncology, McMaster University Medical Center, Hamilton, Ontario, Canada. odamei@mcmaster.ca
authors.forename: Isaac
authors.initials: I
authors.lastname: Odame
authors.forename: Patricia
authors.initials: P
authors.lastname: Li
authors.forename: Loretta
authors.initials: L
authors.lastname: Lau
authors.forename: Wendy
authors.initials: W
authors.lastname: Doda
authors.forename: Mary
authors.initials: M
authors.lastname: Noseworthy
authors.forename: Paul
authors.initials: P
authors.lastname: Babyn
authors.forename: Sheila
authors.initials: S
authors.lastname: Weitzman
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000150:complications* / Q000175:diagnosis / Q000188:drug therapy / Q000401:mortality; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012189:Retrospective Studies