TRIM39-RPP21 is a readthrough transcript located in the MHC region of chromosome 6 that functions as a mediator of interferon response and immune regulation. The gene encodes an E3 ubiquitin ligase involved in innate immune responses 1. Mechanistically, TRIM39-RPP21 participates in interferon signaling pathways central to immune and autoimmune disease pathogenesis 2. Disease associations include cutaneous lupus erythematosus (CLE), where TRIM39-RPP21 variants contribute to dysregulated interferon response and apoptosis regulation 2. The gene is also associated with psoriasis susceptibility, with TRIM39/RPP21 polymorphisms confirmed in Polish populations and contributing to genetic risk scoring models 3. Additionally, a specific 19bp deletion with triple-C insertion (Δ19InsCCC) variant in TRIM39-RPP21 was identified as uniquely shared across Arabian foals diagnosed with juvenile idiopathic epilepsy (JIE), suggesting potential neurological functions 4. Protective variants near TRIM39 demonstrate reduced nasopharyngeal carcinoma risk, indicating tumor-suppressive properties independent of classical HLA alleles 1. The clinical significance lies in TRIM39-RPP21's role as a genetic risk factor for multiple autoimmune and neurological conditions, making it a candidate biomarker for disease susceptibility and potential therapeutic target.