Background: Progressive pseudorheumatoid dysplasia(PPRD) is considered as a degenerative genetic bone disorder. It is caused by loss of function mutation in WNT-1 inducible signaling pathway protein-3(WISP-3) 1 . WISP-3 gene function is required for the normal function of cartilage and skeletal development. The patients are normal at birth and start developing symptoms around 3-6 years of age 2 . The disease is characterised by stiffness, pain, deformity due to enlargement of the ends of short and long bones. Often, such patients are misdiagnosed as Juvenile idiopathic arthritis(JIA). In general, PPRD being considered as non-inflammatory disease, immunosuppressants or disease modifying anti rheumatic drugs(DMARDS) like methotrexate treatment are not used for treatment. Objectives: We report a patient with characteristic findings of PPRD but with coexisting clinical and imaging evidence of inflammation. Methods: 16 year old male boy born of third degree consanguineous asymptomatic parents presented with progressive swelling, deformity of bilateral small and large joints of upper and lower limbs. He also had pain in both hip and knee for past two years. Pain is associated with difficulty in walking and squatting. On examination he had bony enlargement around bilateral elbow, wrist, proximal and distal interphalangeal joints(Figure 1A). He also had restriction of bilateral hip movements and swelling of bilateral knee with effusion. He had exaggerated lumbar lordosis and flexion deformity of bilateral hip, knee. His blood counts, ESR, CRP were normal. Analysis of Knee joint synovial fluid showed cell count of 200/mm3 with no crystals and sterile culture. USG knee showed evidence of synovial thickening with increased power Doppler signals. Skeletal survey showed typical findings of PPRD with enlargement of epiphysis and osteoarthritis changes(Figure 1B). MRI hip showed minimal effusion, synovial thickening, edema with STIR hyperintensity and enlargement of bilateral femoral epiphysis. MRI knee showed minimal effusion, marrow edema in patella(Figure 1C, arrow head), femoral condyle, diffuse synovial thickening with contrast enhancement(Figure 1D, arrow) and deformed patellar contour. Immunological tests showed negative RF, ACPA and positive ANA(Hep2) speckled 4+. Immunoblot for ENA was negative. His ophthalmological evaluation showed no evidence of uveitis. Figure 1. Clinical picture showing typical hand deformity and swelling at bone ends(A), hand radiograph showing epiphyseal enlargement(B), MRI knee T2 STIR showing bone marrow edema(arrow head) in patella(C) and synovial thickening(arrow) with contrast enhancement in fat saturated T1 MRI with contrast. Results: Patient tested positive for homozygous mutation in WISP-3 gene. He was treated with ibuprofen and supportive measures. Orthopedic consultation obtained and planned for hip, knee replacement during follow up. Follow up imaging and acute phase response was advised after three months. Conclusion: Although PPRD was classically described as a degenerative disease, the findings presented in our case show coexisting inflammation. Bone marrow edema in weight bearing areas, synovial effusion may be explained as part of cartilage degeneration like in osteoarthritis but synovial hypertrophy with contrast enhancement, power Doppler signals in ultrasound, ANA positivity may be signs of coexisting inflammatory or autoimmune phenomenon. References: 1Hurvitz JR, Suwairi WM et al. Mutations in the CCN gene family member WISP3 cause progressive pseudorheumatoid dysplasia. Nat Genet. 1999 Sep;23(1):94-8. doi: 10.1038/12699. PMID: 10471507. 2Garcia Segarra N, Mittaz L et al. The diagnostic challenge of progressive pseudorheumatoid dysplasia (PPRD): a review of clinical features, radiographic features, and WISP3 mutations in 63 affected individuals. Am J Med Genet C Semin Med Genet. 2012 Aug 15;160C(3):217-29. doi: 10.1002/ajmg.c.31333. Epub 2012 Jul 12. PMID: 22791401. Disclosure of Interests: None declared