SAA2-SAA4 is a readthrough transcript located on chromosome 11 that encodes an acute-phase reactant protein. The gene functions as part of the innate immune and inflammatory response system. SAA2-SAA4 is expressed in lung tissue as part of a cluster of acute-phase reactant genes (SAA1, SAA2, and SAA2-SAA4) that respond to inflammatory conditions 1. The protein participates in lipid-lipoprotein metabolism and plasma lipoprotein particle remodeling, functioning downstream of multiple signaling pathways including complement and coagulation cascades 2. Clinically, SAA2-SAA4 has emerged as a potential biomarker in several disease states. It was identified as a hub protein in salivary proteomics analysis of medication-related osteonecrosis of the jaw (MRONJ), a serious complication of bisphosphonate therapy, where it participates in pathogenic processes involving macromolecular and lipoprotein complex remodeling 2. Additionally, SAA2-SAA4 expression was significantly altered in children with perinatally acquired HIV-1 experiencing transient viral rebound, with downregulation correlating with decreased CD4/CD8 ratios and serving as a potential immunological marker of disease progression 3. While identified in hepatitis C-related cirrhosis transcriptome studies, validation of SAA2-SAA4 as a diagnostic biomarker in this context showed limited agreement between sequencing and qRT-PCR methods 4.