title: Seasonal distribution of severe ADAMTS13 deficient idiopathic thrombotic thrombocytopenic purpura.
abstract: BACKGROUND
  Idiopathic thrombotic thrombocytopenic purpura (TTP) is a rare yet potentially fatal thrombotic microangiopathy. Severe deficiency of ADAMTS13 activity via autoantibody formation has been associated with idiopathic TTP; however, specific triggers are poorly defined. Previous studies have reported seasonal associations of TTP, with warm-weather seasons appearing to have the strongest predilection. We characterized the seasonal distribution of severe ADAMTS13 deficient idiopathic TTP at our multi-hospital institution.
  
  
  METHODS
  Apheresis records from 2005-2012 were queried for patients with a clinical diagnosis of TTP, accompanying pre-plasmapheresis ADAMTS13 activity <10%, and no other explanations for thrombotic microangiopathy. Date of admission and ADAMTS13 activity were collected. Both initial episodes and relapses in patients whose initial episodes occurred since 2005 were included in the analysis. Goodness-of-fit chi-square analysis was performed and statistical significance was defined as p<0.05.
  
  
  RESULTS
  Of 237 consecutive new patients with a suspected clinical diagnosis of TTP, 73 patients met inclusion criteria and had a total of 110 unique presentations for either initial TTP episodes or TTP relapses. Sixteen patients had 37 relapses of their idiopathic TTP (range 1-7). No statistically significant seasonal or monthly associations were identified with either initial or any TTP episodes.
  
  
  CONCLUSIONS
  A seasonal association of severe ADAMTS13 deficient idiopathic TTP was not observed. Unknown variables may explain previous observations of seasonal associations of idiopathic TTP in other regions of the United States. Thus, individual institutions should characterize their own seasonal distributions of idiopathic TTP as part of the exploration of possible disease triggers in their respective areas.
authors.affiliation: The Institute for Transfusion Medicine, Pittsburgh, Pennsylvania; Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Jay S
authors.initials: JS
authors.lastname: Raval
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Harm
authors.forename: Marian A
authors.initials: MA
authors.lastname: Rollins-Raval
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Kiss
mesh_terms: D051722:ADAM Proteins / Q000097:blood / Q000172:deficiency*; D000071120:ADAMTS13 Protein; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood / Q000209:etiology*; D012307:Risk Factors; D012621:Seasons; D014807:Vitamin D / Q000097:blood
chemical_list: D014807:Vitamin D; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human
keywords: TTP; distribution; season; seasonal; thrombotic thrombocytopenic purpura