Abstract Background: The severity of rheumatoid arthritis (RA) is accompanied by the intensity of the inflammation and the joint damage. PTX-3 is a multifunctional protein with complex regulatory roles in inflammation and extracellular matrix organization and it is believed to more precisely present the actual inflammatory condition. Aim of Study: The aim of the current work was to detect the serum PTX-3 level in RA cases and correlate its level with the clinical features, disease activity score (DAS28) and musculoskeletal ultrasound (MSUS) score. Patients and Methods: Forty RA cases and 40 matched age and sex normal controls were comprised. Entire cases were subjected to history taking and clinical examination. Laboratory investigations, comprising CBC, ESR, CRP, RF, anti-CCP, random blood sugar, and serum PTX3 were estimated in all participants. DAS -28 assessment and Musculoskeletal ultrasound for hands and feet according to novel 7 joint US score were done in RA cases. Results: Serum PTX3 level were significantly increased in RA cases in comparison with control group. There was a significant positive correlation between serum PTX3 level and duration of morning stiffness, DAS 28 parameters. There was a significant positive association between serum level of PTX-3 and Synovitis GSUS score, Synovitis PDUS score, Tenosynovitis GSUS score and Tenosynovitis PDUS score. Conclusion: Patients with RA exhibits a significant ele-vation in serum PTX3. Serum PTX3 level significantly correlates with clinical features, disease activity and MSUS parameter of inflammation and could act as a potentially efficient marker with for assessment of disease activity in RA