title: The methotrexate polyglutamate assay supports the efficacy of methotrexate for severe inflammatory skin disease in children.
abstract: BACKGROUND
  The methotrexate (MTX) polyglutamate assay has been validated in adults with arthritis.
  
  
  OBJECTIVE
  We sought to assess clinical response rates and the value of the methotrexate polyglutamate assay in MTX-treated children with inflammatory skin diseases.
  
  
  METHODS
  In this retrospective review, 46 MTX-treated children with a diagnosis of atopic dermatitis, psoriasis, or psoriasis-eczema overlap were serially assessed with the methotrexate polyglutamate assay.
  
  
  RESULTS
  In all, 38 children (83%) achieved good to excellent response: 27 (59%) within 12 weeks and 11 (24%) after dose-adjustment. Good to excellent responses were highest for psoriasis/overlap: 15 of 16 (94%), compared with 23 of 30 (77%) with atopic dermatitis. Mean maximum polyglutamate levels were 31.5 nmol/L for responders versus 18.1 nmol/L for nonresponders (P = .035). This difference was also significant for the subset with atopic dermatitis, but not for those with psoriasis/overlap. After dose modification, late responders ultimately achieved a significantly higher mean maximum methotrexate polyglutamate assay (41.9 nmol/L) compared with nonresponders (P = .002).
  
  
  CONCLUSIONS
  Retrospective design and small sample size were limitations.
  
  
  CONCLUSIONS
  MTX is an effective treatment for the majority of children with inflammatory skin diseases, but a subset requires dose modification to achieve good to excellent response. Methotrexate polyglutamate assay levels reflect response to treatment, but are most useful to support dose modification among children who fail to respond within 12 weeks.
authors: Saint Louis University School of Medicine, Saint Louis, Missouri.
authors: Syed I
authors: SI
authors: Rahman
authors: Department of Pediatrics, Division of Dermatology, SSM Cardinal Glennon Children's Medical Center, Saint Louis, Missouri. Electronic address: esiegfri@slu.edu.
authors: Elaine
authors: E
authors: Siegfried
authors: Dermatology and Laser of Alabama, Birmingham, Alabama.
authors: Katherine H
authors: KH
authors: Flanagan
authors: Saint Louis University Center for Outcomes Research, Saint Louis, Missouri.
authors: Eric S
authors: ES
authors: Armbrecht
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003872:Dermatitis; D003876:Dermatitis, Atopic / Q000175:diagnosis / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004485:Eczema / Q000175:diagnosis / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D011565:Psoriasis / Q000175:diagnosis / Q000188:drug therapy*; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D011099:Polyglutamic Acid; C014085:methotrexate polyglutamate; D008727:Methotrexate
keywords: AD; MTX; atopic dermatitis; methotrexate; methotrexate polyglutamate assay; overlap; pediatric/children; psoriasis