Anti-citrullinated Protein Antibody-positive Arthralgia Associated with an L110P-E148Q Double Heterozygote: A Case-based Review.

A 42-year-old woman with positive anti-citrullinated protein antibody (ACPA) and rheumatoid factor (RF) levels exhibited arthralgia, but she did not fulfill the criteria for rheumatoid arthritis (RA). Subsequently, the patient exhibited episodic monoarthritis with a remarkable response to colchicine. An analysis of the MEFV gene identified heterozygous variants, L110P and E148Q, thus indicating a colchicine-responsive autoinflammatory condition. The patient was later diagnosed with RA and achieved remission with abatacept and colchicine. This case illustrates that ACPA-positive arthralgia evolves into RA through an autoinflammatory mechanism, thereby underscoring the diagnostic difficulties arising from the convergence of both autoimmune and autoinflammatory characteristics.