title: Reactivation and risk of sequelae in Langerhans cell histiocytosis.
abstract: OBJECTIVE
  To evaluate disease reactivation in patients with Langerhans cell histiocytosis (LCH) and its impact on adverse sequelae.
  
  
  METHODS
  A retrospective evaluation of 300 patients diagnosed with LCH between 1987 and 2002 with complete response to initial treatment was performed.
  
  
  RESULTS
  Mean age at diagnosis was 5.3 years. With a mean follow-up of 4.8 years, reactivation of the disease occurred in 29.7% (89/300) of the patients, with two or more reactivations in 34.8% (31/89) of those. Reactivation occurred in 17.4, 36.8, 46.5, and 53.5% of the patients with single-system unifocal disease (Group A: 161 patients), single-system multifocal disease (Group B: 53 patients), multi-system disease without (Group C: 58 patients), and with (Group D: 28 patients) risk-organ involvement, respectively. The differences between the incidence rates of Groups A and B (P < 0.0004), A and C (P < 0.0001), and A and D (P < 0.0001) were highly significant. The most common reactivation sites involved were bone, middle ear, and skin; reactivation was rare in risk organs (9.5%). The median time between initial complete response and the first reactivation episode was 1 year for Group A, 1.3 years for Group B, and 9 months for Groups C and D. Most reactivation episodes (88%) occurred within the first 2 years of follow-up. Adverse sequelae were recognized in 242/300 patients: 71% (49/69) of patients with and 25.4% (44/173) without reactivations developed these adverse sequelae (P < 0.0001), respectively. Sites most commonly showing sequelae were bone, middle ear, and hypothalamus (Diabetes Insipidus).
  
  
  CONCLUSIONS
  Incidence of reactivation correlates with the stage of the disease at diagnosis. Incidence of sequelae correlates with the occurrence of reactivations.
authors.affiliation: Department of Hematology/Oncology, Hospital de Niños Superiora Sor María Ludovica, La Plata, Argentina.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pollono
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Rey
authors.forename: Antonio
authors.initials: A
authors.lastname: Latella
authors.forename: Diego
authors.initials: D
authors.lastname: Rosso
authors.forename: Guillermo
authors.initials: G
authors.lastname: Chantada
authors.forename: Jorge
authors.initials: J
authors.lastname: Braier
mesh_terms: D000293:Adolescent; D001118:Argentina / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006646:Histiocytosis, Langerhans-Cell / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index