Sm/RNP Antibodies

Smith (Sm) and Ribonucleoprotein (RNP) antibodies are specific types of ENAs. Anti-Sm is highly specific for Systemic Lupus Erythematosus (SLE), though only present in ~20-30% of patients. Anti-RNP is characteristic of Mixed Connective Tissue Disease (MCTD) when present in high titers without other specific antibodies, but can also be found in SLE and other autoimmune conditions.