RPP38 is a protein subunit of ribonuclease P (RNase P) and ribonuclease MRP (RNase MRP), two related ribonucleoprotein complexes essential for RNA processing 1. As a component of RNase P, RPP38 participates in generating mature tRNA molecules by cleaving their 5' leader sequences 2. RPP38 also associates with the RNase MRP complex, which cleaves precursor rRNA to form the 5' end of 5.8S rRNA 3. Structurally, RPP38 contains a cluster of basic amino acids and localizes to the nucleolus and coiled bodies, where it is uniformly distributed throughout the nucleolus 2. The protein binds to K-turn motifs in RNase P RNA, with specific amino acid residues (Lys35, Asn38, Glu39) interacting with conserved RNA base pairs 4. Clinically, RPP38 is a major autoantigen targeted by autoantibodies in systemic sclerosis (SSc), an autoimmune rheumatic disease 5. Anti-Rpp38 autoantibodies are detected in approximately 5.4% of limited cutaneous SSc patients and are absent in healthy controls, making Rpp38 a promising biomarker for enhanced serological diagnosis of SSc 6. The autoimmune targeting of Rpp38 and other RNase MRP/P subunits suggests potential pathogenic mechanisms in scleroderma-associated autoimmunity 7.