title: Reactivations in multisystem Langerhans cell histiocytosis: data of the international LCH registry.
abstract: OBJECTIVE
  To assess multisystem Langerhans cell histiocytosis reactivation and its impact on morbidity and mortality.
  
  
  METHODS
  Retrospective analysis of 335 patients with MS-LCH and documented complete disease resolution (NAD1).
  
  
  RESULTS
  The probability of a reactivation within 5 years of NAD1 was 46%. The first reactivation occurred within 2 years after NAD1 in most of the patients. Of 134 events, 35% were confined to skeleton, 24% were single-system nonbony lesions, 24% were multisystem reactivations without risk-organ involvement, and 10% with risk-organ involvement. In 7%, the location was unspecified. Only 3 deaths (2.2%) were documented within the context of a first reactivation. Second disease resolution (NAD2) was achieved in 85% of the cases. The probability of a second reactivation within 5 years of NAD2 was 44%. The risk for permanent consequences in patients with reactivations was higher, compared with patients without reactivation (RHR 2.2, P = .046).
  
  
  CONCLUSIONS
  Reactivation is a frequent and early event in MS-LCH, but involvement of risk organs at reactivation is rare and mortality is minimal. However, reactivations increase the risk for permanent consequences by about 2-fold. Prospective trials targeting reduction of acute morbidity and permanent disabilities through nontoxic treatment of the reactivations are warranted.
authors.affiliation: St Anna Children's Hospital, Vienna, Austria. mail:milen.minkov@stanna.at.
authors.forename: Milen
authors.initials: M
authors.lastname: Minkov
authors.forename: Manuel
authors.initials: M
authors.lastname: Steiner
authors.forename: Ulrike
authors.initials: U
authors.lastname: Pötschger
authors.forename: Maurizio
authors.initials: M
authors.lastname: Aricò
authors.forename: Jorge
authors.initials: J
authors.lastname: Braier
authors.forename: Jean
authors.initials: J
authors.lastname: Donadieu
authors.forename: Nicole
authors.initials: N
authors.lastname: Grois
authors.forename: Jan-Inge
authors.initials: JI
authors.lastname: Henter
authors.forename: Gritta
authors.initials: G
authors.lastname: Janka
authors.forename: Kenneth
authors.initials: K
authors.lastname: McClain
authors.forename: Sheila
authors.initials: S
authors.lastname: Weitzman
authors.forename: Kevin
authors.initials: K
authors.lastname: Windebank
authors.forename: Stephan
authors.initials: S
authors.lastname: Ladisch
authors.forename: Helmut
authors.initials: H
authors.lastname: Gadner
mesh_terms: D002986:Clinical Trials as Topic; D020790:Diabetes Insipidus, Neurogenic / Q000175:diagnosis / Q000473:pathology; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000175:diagnosis* / Q000401:mortality* / Q000503:physiopathology; D006801:Humans; D007223:Infant; D007391:International Cooperation; D008297:Male; D011336:Probability; D011446:Prospective Studies; D012008:Recurrence; D012042:Registries; D012189:Retrospective Studies; D012306:Risk; D016896:Treatment Outcome