Discussion
RA is usually diagnosed based on the classification of the American college of rheumatology (5). According to the classification, A score of more or six is usually indicating RA, the classification includes features like Involved joint type, duration and serology markers such as CRP, ESR, RF and anti-CCP. When the patient still exhibit symptoms and signs of RA but his serological markers are negative this is an indication of seronegative rheumatoid arthritis. RA has long been recognized as an extremely heterogeneous disorder of immune dys-regulation. Despite an ever-growing appreciation of the role of circulating autoantibodies in the progress of ’seropositive’ disease, the pathogenesis of sero-negative RA remains poorly understood (1).
The clinical presentation and scenario of this case can fit with many diagnoses such as undifferentiated arthritis which is an overlap syndrome with RA and not fit well known clinical disease categories ( e.g reactive arthritis and sero-negative RA) (8, 9). Although, synovial knee biopsy confirmed the diagnosis. other possible diagnosis overlaps with this patient condition include reactive arthritis, but the absence of infection exclude the diagnosis as the swelling and joint pain in reactive arthritis mainly triggered by infection (10). Psoriatic arthritis includes similar clinical features such as joints pain and stiffness and the diagnosis is primarily based on the clinical phenotype due to the diversity of the associated features which include nail and skin disease, uveitis, dactylitis and osteitis (11). And these skin manifestations were not presented in this case.
The synovial biopsy is not usually used for routine diagnostic or therapeutic purpose in RA patients (12). However, synovial tissue examination can assist in the diagnosis of some joint infection. Although there is no diagnostic role in acute RA, although, synovial tissue analysis that can provide significant prognostic information, recent studies have shown that examined mediators of joint damage and synovial tissue inflammation were found to be linked with unfavourable radiological and clinical outcomes (13).
Although genetic variation has long been supposed to account for around 60% of RA risk (14), however recent reports indicates that this figure for heritability may be significantly lower in sero-negative RA (15). It follows that environmental factors such as smoking should play a more essential role in seronegative RA, but much has yet to be understood in this area (16, 17).