The pathogenesis of rheumatoid arthritis in radiological studies. Part I: Formation of inflammatory infiltrates within the synovial membrane and I. Sudoł-Szopińska, K. Zaniewicz-Kaniewska, A. Warczyńska, G. Matuszewska, F. Saied, W. Kunisz The pathogenesis of rheumatoid arthritis in radiological studies. Part II: Imaging studies in rheumatoid arthritis.

In the recent years, musculoskeletal ultrasound (US) has been developing rapidly as a method evaluating the intensity of the inflammatory process in inflammatory joint diseases including rheumatoid arthritis (RA). The series of articles entitled: The pathogenesis of rheumatoid arthritis in radiological studies (parts 1 and 2)(1, 2) enable a deeper insight into the relation between the disease progression and changes visible on imaging such as US and magnetic resonance imaging (MRI). As the authors of the articles emphasize, these methods are important for the determination of the exact natural course of the disease, diagnostic differentiation of RA as well as monitoring its activity. The changes which could suggest RA in US exams are pathologies of the synovial membrane of the joints and tendon sheaths, joints and tendon sheaths effusion as well as erosions. On the other hand, the presence of enthesitis suggests the inflammation of the peripheral joints in the course of spondyloarthropathy such as psoriatic arthritis or ankylosing spondylitis. In the study of Narvaez et al., enthesitis, extensive bone marrow edema of the hand and wrist bones, diffuse soft tissue swelling of the hand and wrist and, to a certain extent, the involvement of the flexor tendons in MRI distinguished psoriatic arthritis from RA(3). In the US examination, at the early stage of arthritis, it is essential to check some joints for the presence of lesions which typically indicate that RA may develop in the later course of the disease. The research of Filer et al. shows that during the first US exam of the patients who developed RA, the following were diagnosed: subclinical synovitis of wrists, elbows, knees, ankle joints, metatarsophalangeal joints (MTP) and metacarpophalangeal joints (MCP)(4). The inflammation of large joints as well as proximal interphalangeal joints visualized during the US examination were of low prognostic value. The most important prognostic factor in RA development was the diagnosis of synovitis in the grey-scale US examination of the wrists and MCP joints as well as MTP joints synovitis in the power Doppler US. Therefore, US examinations of the wrists, MCP and MTP joints should always be performed in patients suffering from early arthritis with high-risk of RA development. In addition, it needs to be mentioned that joints ultrasound in patients receiving pharmacological treatment for early RA, facilitates the detection of minimum inflammatory activity with greater sensitivity than physical examination. Synovial hypertrophy with hypervascularization in power Doppler US enables the recognition of active inflammation in patients in a stage of clinical remission. In a study based on 48 patients with early RA, the US examination confirmed the clinical remission in 67% of the subjects(5). Simultaneously, the exacerbation of the disease occurred in 47% of the patients in remission of early arthritis in whom the power Doppler signal was present. Out of the patients in whom there was no power Doppler signal in the synovial membrane, the disease exacerbation occurred in merely 20% of cases.