Rheumatoid arthritis as a clinical and immunological syndrome: focus on the seronegative subtype of the disease

Rheumatoid arthritis (RA) is the most common immune mediated (autoimmune) rheumatic disease, manifested by chronic erosive arthritis and systemic internal organ damage. Currently, RA is considered as a syndrome characterized by clinical and pathogenetic heterogeneity associated with a variety of mechanisms of pathological activation of innate and acquired immunity, determining the variability of the course and outcome of the inflammatory process and effectiveness of therapy. Based on the detection or absence of rheumatoid factor (RF) IgM and antibodies to cyclic citrullinated peptides (ACCP), RA can be conventionally divided into two subtypes (phenotypes): seropositive RA and seronegative RA, but thanks to improvement of laboratory diagnostic methods the spectrum of autoantibodies detected in RA has increased significantly. Diagnosis of seronegative RA based on classification (rather than diagnostic) criteria can be difficult, especially in the early stages of the disease, and the diagnosis is made only during long-term follow-up of patients. It complicates the timely prescription of adequate anti-inflammatory therapy. This article summarizes the data on genetic predisposition, immunopathogenesis, biomarkers, clinical spectrum, instrumental diagnosis and pharmacotherapy of seronegative RA.