AntiRNP

AntiRNP refers to autoantibodies directed against ribonucleoprotein particles, most commonly the U1 small nuclear ribonucleoprotein (U1 snRNP) complex. The U1 snRNP is part of the spliceosome, a cellular machine that processes pre‑mRNA. Autoantibodies target components of this complex, such as U1-70K, U1-A, and U1-C, and are detected in various autoimmune diseases.

Clinically, anti-U1 RNP antibodies are most closely associated with mixed connective tissue disease (MCTD), where they are considered a hallmark serologic marker. In MCTD, high-titer anti-U1 RNP antibodies often accompany a characteristic combination of symptoms, including arthritis, myositis, Raynaud phenomenon, swollen hands, and esophageal dysmotility. Anti-U1 RNP can also be present in individuals with other connective tissue diseases, such as systemic lupus erythematosus or systemic sclerosis, usually in less prominent or overlapping forms. Therefore, while anti-RNP positivity supports a connective tissue disease diagnosis, it must be interpreted in the context of clinical features and other laboratory findings.

Diagnosis typically involves autoantibody testing using immunoassays, immunoprecipitation, or immunoblot techniques. Anti-U1 RNP is often included in extractable nuclear antigen (ENA) panels alongside other antibodies. The presence of anti-RNP antibodies aids classification and can help guide monitoring for overlapping organ involvement, but it does not by itself determine treatment.

Management is directed at the clinical manifestations and organ involvement, using standard approaches for the underlying disease (for example, corticosteroids or immunosuppressants for inflammatory myopathy, arthritis, or esophageal involvement). There is no therapy that specifically targets anti-RNP antibodies.