title: Mega os trigonum in progressive pseudorheumatoid dysplasia.
abstract: BACKGROUND
  Progressive pseudorheumatoid dysplasia (PPRD), a noninflammatory condition, needs to be differentiated diagnostically from juvenile rheumatoid arthritis (JRA).
  
  
  OBJECTIVE
  Demonstration of an unusually large and often early-appearing os trigonum helps distinguish PPRD from JRA.
  
  
  METHODS
  Ankle images in four children with PPRD were reviewed.
  
  
  RESULTS
  The os trigonum was abnormally enlarged in all PPRD subjects and was shown to have appeared or fused earlier than normal in two subjects.
  
  
  CONCLUSIONS
  A large and early os trigonum ossification helps differentiate PPRD from JRA.
authors.affiliation: Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA. oestreich.ae@chmcc.org
authors.forename: Alan E
authors.initials: AE
authors.lastname: Oestreich
mesh_terms: D001171:Arthritis, Juvenile / Q000000981:diagnostic imaging*; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D010009:Osteochondrodysplasias / Q000000981:diagnostic imaging*; D011859:Radiography; D013628:Talus / Q000000981:diagnostic imaging* / Q000473:pathology*