ACCA

Definition & Etymology

Anti-Carbamylated Protein Antibodies (ACarP), occasionally abbreviated as ACCA, are a class of autoantibodies that target proteins which have undergone carbamylation. Carbamylation is a non-enzymatic, post-translational modification where a cyanate molecule covalently binds to primary amino groups (e.g., lysine residues) on a protein. This process alters the protein’s structure and charge, creating neoantigens that can trigger an autoimmune response. The term derives from the chemical process of carbamylation, which is often accelerated in inflammatory environments where urea concentrations may increase and break down into cyanate.

Clinical Significance

ACarP are clinically significant serological biomarkers, primarily in the field of rheumatology. Their main role is in the diagnosis and prognosis of rheumatoid arthritis (RA). They are present in approximately 45-50% of RA patients, including a subset of individuals who test negative for the more established markers like Rheumatoid Factor (RF) and Anti-Citrullinated Protein Antibodies (ACPA). This makes ACarP a valuable complementary diagnostic tool. Furthermore, the presence of ACarP, particularly in high titers, is associated with a more aggressive disease course, including more severe joint erosion and radiographic progression, thus providing important prognostic information.

Related Conditions

The foremost condition associated with ACarP is Rheumatoid Arthritis (RA). They are considered part of the spectrum of autoantibodies specific to RA and are used to stratify patients. While strongly linked to RA, low levels of ACarP have also been detected in other systemic autoimmune conditions, such as Systemic Lupus Erythematosus (SLE), Sjögren’s syndrome, and Psoriatic Arthritis. However, their diagnostic and prognostic utility in these other diseases is not as well-defined as it is for RA. They are most useful when assessing patients with undifferentiated arthritis to help predict progression to definite RA.

Key Takeaways

• Specific Autoantibody: ACarP are autoantibodies that recognize carbamylated proteins, which are structurally altered proteins that the immune system mistakes as foreign.
• RA Biomarker: They serve as a crucial diagnostic and prognostic marker for rheumatoid arthritis, particularly useful in identifying patients who are seronegative for RF and ACPA.
• Prognostic Value: The presence of ACarP is often linked to more severe disease outcomes in RA, including increased joint damage and functional disability.

Note: This content is for informational purposes only and does not substitute for professional medical advice. Always consult your doctor for diagnosis and treatment.