title: Nationwide survey of single-system single site Langerhans cell histiocytosis in Japan.
abstract: BACKGROUND
  Since neither a standard treatment nor a protocol study for single-system single site (SS-s)-type Langerhans cell histiocytosis (LCH) exists, we conducted a nationwide survey in Japan to clarify the epidemiology and clinical outcome of this subtype.
  
  
  METHODS
  Questionnaires regarding the clinical course of children with SS-s-type LCH diagnosed between 1995 and 2006 were sent to all members of the Japanese Society of Pediatric Hematology.
  
  
  RESULTS
  One hundred forty-six children with histologically proven SS-s LCH were evaluable. The most frequently affected organ was bone (82%), followed by skin (12%). Few patients (14%) had a CNS-RISK lesion defined by the Histiocyte Society. Patients with a skin lesion were diagnosed at a significantly younger age than patients with a bone lesion (median: 6 months vs. 5 years 11 months, P < 0.001). The treatment regimen varied, but one-third of the patients in total and 71% of patients with a CNS-RISK lesion received chemotherapy that did not include etoposide. All but one patient attained remission. Ten patients (7%) showed reactivation. Of these, all eight with an initial bone lesion only exhibited reactivation in the bone(s). One patient with an initial skin lesion exhibited reactivation in the thymus. None of the patients died from disease progression or treatment complications.
  
  
  CONCLUSIONS
  Our retrospective study, in which a relatively large proportion of the patients received chemotherapy, reveals that patients with SS-s LCH have a good prognosis. A prospective study should be conducted to confirm this and to identify the most effective and least toxic therapy for SS-s LCH.
authors.affiliation: Department of Pediatrics, Jichi Medical University School of Medicine, Shimotsuke, Japan. akira@jichi.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Morimoto
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ishida
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Suzuki
authors.forename: Shouichi
authors.initials: S
authors.lastname: Ohga
authors.forename: Yoko
authors.initials: Y
authors.lastname: Shioda
authors.forename: Yuri
authors.initials: Y
authors.lastname: Okimoto
authors.forename: Kazuko
authors.initials: K
authors.lastname: Kudo
authors.forename: Eiichi
authors.initials: E
authors.lastname: Ishii
mesh_terms: D000293:Adolescent; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D005260:Female; D006306:Health Surveys; D006646:Histiocytosis, Langerhans-Cell / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008297:Male; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome