title: Subclinical enthesitis in nail psoriasis patients: a case-control study.
abstract: BACKGROUND
  Patients with nail psoriasis have a higher prevalence of psoriatic arthritis; however, the pathogenetic relationship between these two disorders is as yet unclear. Entheses have been suggested as disease epicenter, which might explain the pathogenesis on an anatomical level.
  
  
  OBJECTIVE
  To contribute to the elucidation of the hypothesis as regards the anatomical link between nail psoriasis and psoriatic arthritis, with the extensor enthesis of the distal interphalangeal joint as the epicenter.
  
  
  METHODS
  We conducted a cross-sectional cohort study, visualizing the distal interphalangeal (DIP) joints entheses of patients with fingernail psoriasis (n = 54), psoriasis patients without nail involvement (n = 32), and healthy controls (n = 32) using three-dimensional ultrasound. Patients with nail psoriasis underwent repeat imaging studies after one year.
  
  
  RESULTS
  Individuals with nail psoriasis had significantly thicker radial entheses than psoriasis patients without nail involvement. However, there were no significant differences in entheseal thickness between adjacent nails that were affected and those that were not (1.297 mm vs. 1.253 mm, p = 0.13). Follow-up after one year showed no significant differences in entheseal thickness in correlation with nail psoriasis activity.
  
  
  CONCLUSIONS
  The present study provides evidence for subclinical enthesitis at the level of the DIP joint in patients with nail psoriasis. However, an anatomical correlation between nail psoriasis and psoriatic arthritis could not be confirmed.
authors.affiliation: Department of Dermatology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Karlijn M G
authors.initials: KM
authors.lastname: Klaassen
authors.affiliation: Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Marieke J M
authors.initials: MJ
authors.lastname: Ploegmakers
authors.affiliation: Department of Dermatology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Peter C M
authors.initials: PC
authors.lastname: van de Kerkhof
authors.affiliation: Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Willemijn M
authors.initials: WM
authors.lastname: Klein
authors.affiliation: Department of Dermatology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Marcel C
authors.initials: MC
authors.lastname: Pasch
mesh_terms: D000328:Adult; D017677:Age Distribution; D015535:Arthritis, Psoriatic / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D058070:Asymptomatic Diseases / Q000453:epidemiology; D016022:Case-Control Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009260:Nail Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D009426:Netherlands / Q000453:epidemiology; D011565:Psoriasis / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D014463:Ultrasonography / Q000706:statistics & numerical data