title: Multifocal pigmented villonodular synovitis in a child: A case report.
abstract: BACKGROUND
  Pigmented villonodular synovitis (PVNS) is a rare, benign proliferative disorder of the synovial membrane that typically presents in adults and affects a single joint. Multifocal PVNS is very rare, particularly in childhood. We reported a rare case of multifocal PVNS affecting over 20 joints in a child.
  
  
  METHODS
  A 7-year-old female patient had a 6-month history of multifocal joints swelling with mild pain. She was diagnosed as polyarticular juvenile idiopathic arthritis at a local hospital. Naproxen, methotrexate, infliximab, and pavlin were used to treat the patient for 2 months. However, the treatment had no effect, the joints swelling remained. The patient was then transferred to our hospital. Physical examination revealed multiple joints swelling, especially in the shoulders joints. Puncture fluid from a shoulder joint was bloody. Magnetic resonance imaging (MRI) revealed synovial thickening and hemosiderin deposition. Biopsy of joint synovium found villous nodules, the invasion of foam cells, and hemosiderin deposition. By collecting all of the evidence, the diagnosis of PVNS was confirmed.
  
  
  CONCLUSIONS
  PVNS was easily misdiagnosed as rheumatoid arthritis and the formal treatment was usually delayed. This case described here is the first case of PVNS involving such a large numbers of joints that has been reported in the literature.
authors.affiliation: Department of Pediatrics Key Laboratory of Ministry of Education for Obstetric & Gynecologic and Pediatric Diseases and Birth Defects, West China Second University Hospital, Sichuan University, Chengdu, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhao
authors.forename: Kaiyu
authors.initials: K
authors.lastname: Zhou
authors.forename: Yimin
authors.initials: Y
authors.lastname: Hua
authors.forename: Yifei
authors.initials: Y
authors.lastname: Li
authors.forename: Dezhi
authors.initials: D
authors.lastname: Mu
mesh_terms: D000367:Age Factors; D002648:Child; D005260:Female; D006801:Humans; D007596:Joints / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D013583:Synovial Membrane / Q000000981:diagnostic imaging / Q000473:pathology; D013586:Synovitis, Pigmented Villonodular / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology