{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T10:49:29Z","timestamp":1785408569323,"version":"3.56.0"},"reference-count":23,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T00:00:00Z","timestamp":1776211200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["2025.06234.BDANA"],"award-info":[{"award-number":["2025.06234.BDANA"]}]},{"award":["2025.06234.BDANA"],"award-info":[{"award-number":["2025.06234.BDANA"]}],"id":[{"id":"https:\/\/ror.org\/00snfqn58","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Juvenile idiopathic arthritis (JIA) represents the most common cause of chronic arthritis in childhood; however, not all early-onset arthropathies are inflammatory in origin. We report the case of a 4-year-old girl initially diagnosed with oligoarticular JIA and treated with methotrexate followed by a tumor necrosis factor inhibitor, without significant clinical improvement and despite persistently normal inflammatory markers. Clinical reassessment raised suspicion of a non-inflammatory arthropathy, supported by characteristic radiographic findings including metaphyseal flaring of the distal femora and proximal tibiae. Genetic analysis identified compound heterozygous pathogenic variants in the PRG4 gene, confirming the diagnosis of camptodactyly\u2013arthropathy\u2013coxa vara\u2013pericarditis (CACP) syndrome (OMIM #208250). PRG4 encodes lubricin, a mucin-like glycoprotein essential for boundary lubrication of articular cartilage and maintenance of synovial joint homeostasis. Loss-of-function variants disrupt joint lubrication, leading to mechanical synovial hyperplasia and chronic non-inflammatory joint effusion. This case highlights common diagnostic pitfalls in pediatric rheumatology and underscores the importance of considering genetic causes of chronic arthropathy when clinical and laboratory features are atypical for inflammatory disease. Early molecular diagnosis prevents unnecessary immunosuppressive therapy and enables appropriate multidisciplinary management.<\/jats:p>","DOI":"10.3390\/ijms27083534","type":"journal-article","created":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T14:02:33Z","timestamp":1776261753000},"page":"3534","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["PRG4-Related Camptodactyly\u2013Arthropathy\u2013Coxa Vara\u2013Pericarditis Syndrome Mimicking Juvenile Idiopathic Arthritis: A Case-Based Review"],"prefix":"10.3390","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3508-2304","authenticated-orcid":false,"given":"Nataliya","family":"Tkachenko","sequence":"first","affiliation":[{"name":"Department of Genetics, Hospital Divino Espirito Santo of Ponta Delgada, Av. D. Manuel I, 9500-782 Ponta Delgada, Azores, Portugal"},{"name":"Faculty of Sciences and Technology, University of the Azores (UAc), 9500-321 Ponta Delgada, Azores, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7028-4657","authenticated-orcid":false,"given":"Cl\u00e1udia","family":"Castelo Branco","sequence":"additional","affiliation":[{"name":"Department of Genetics, Hospital Divino Espirito Santo of Ponta Delgada, Av. D. Manuel I, 9500-782 Ponta Delgada, Azores, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"77","DOI":"10.3109\/03009742.2015.1085085","article-title":"Camptodactyly-arthropathy-coxa vara-pericarditis syndrome: A mimicker of juvenile idiopathic arthritis","volume":"45","author":"Madhusudan","year":"2016","journal-title":"Scand. J. 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