Introduction
Rheumatoid arthritis has widely been known as a highly heterogeneous disorder of Immune dys-regulation (1, 2), Rheumatoid factor (RF) is an autoantibody, and is been used in the diagnosis of rheumatoid arthritis for years, recently, Anti-cyclic citrullinated peptide antibody (ACPA) has gained more attention, as a valuable and significant marker in predicting and diagnosing of RA (3). Both RF and ACPA have the same sensitivity, however, ACPA much more specific in the diagnosis of RA (4).
Nowadays, seronegative RA has become a moving target, reflecting both new modification in RA categorization (5), and an evolving understanding of diseases-antibodies association (5). The proportion of the RA patients which is reportedly sero-negative for both ACPA and RF ranges between 0.1-0.48 (6).
ACPA and RF have been recognized as poor prognostic markers of RA, and both are used evidence to justify the use of intensive therapy in seropositive RA patients (SPRA) (7). The report aims to draw attention to unusual presentation of RA in a young sero-negative patient.