title: The epidemiology of lymphangioleiomyomatosis in Japan: a nationwide cross-sectional study of presenting features and prognostic factors.
abstract: OBJECTIVE
  To evaluate the characteristics and prognostic factors of Japanese patients with lymphangioleiomyomatosis (LAM).
  
  
  METHODS
  A nationwide survey to identify patients with LAM was conducted by questionnaire. Survival probability was estimated using the Kaplan-Meier method, and the prognostic factors were analysed by Cox regression.
  
  
  RESULTS
  Data were collected on 173 patients with pulmonary LAM. The major presenting features were pneumothorax (43%) and exertional dyspnoea (37%). The survival probabilities for patients presenting with exertional dyspnoea (Group A) were 85%, 60% and 47% after 5, 10 and 15 years, respectively, and for patients presenting with pneumothorax (Group B) were 95%, 89% and 89%, respectively. Although the age at symptom onset was higher among patients in Group A than in Group B, Cox regression revealed that the presenting feature was a prognostic factor independent of age at symptom onset (Group A/B hazard ratio = 5.732, P < 0.01). In the subgroup of patients whose initial FEV(1) was >1000 mL, or FEV(1)/FVC >40%, or %DL(CO) >40%, the rate of deterioration in these tests was greater in Group A than in Group B (P < 0.01 for FEV(1), P < 0.05 for FEV(1)/FVC and %DL(CO)).
  
  
  CONCLUSIONS
  There are two possible subgroups of LAM patients. One subgroup that presented with pneumothorax, had onset of symptoms at a younger age and a more favourable prognosis; the other presented with exertional dyspnoea, had onset of symptoms at an older age and a poorer prognosis.
authors.affiliation: Department of Internal Medicine, School of Medicine, Shinshu University, Matsumoto, Japan.
authors.forename: Mie
authors.initials: M
authors.lastname: Hayashida
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Seyama
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Inoue
authors.forename: Keisaku
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Keishi
authors.initials: K
authors.lastname: Kubo
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D006801:Humans; D007564:Japan / Q000453:epidemiology; D018192:Lymphangioleiomyomatosis / Q000175:diagnosis / Q000453:epidemiology* / Q000401:mortality; D011379:Prognosis; D012129:Respiratory Function Tests; D016019:Survival Analysis