NT5C1A (5'-nucleotidase, cytosolic IA) catalyzes the hydrolysis of ribonucleotide and deoxyribonucleotide monophosphates, releasing inorganic phosphate and the corresponding nucleoside, with AMP as the major substrate but also hydrolyzing dCMP and IMP 1234. The enzyme functions in nucleotide metabolism pathways including AMP catabolism and adenosine metabolism within the cytosol. NT5C1A has gained significant clinical importance as an autoimmune target, with anti-NT5C1A autoantibodies serving as a key biomarker for inclusion body myositis (IBM), detected in 33-76% of IBM patients 5. These autoantibodies are found with high specificity for IBM compared to other inflammatory myopathies, though they can occur in other autoimmune conditions including dermatomyositis (15%), Sjögren's syndrome (23%), and systemic lupus erythematosus (14%) 5. In IBM patients, anti-NT5C1A seropositivity is associated with more severe muscle weakness and may correlate with specific pathological features including cytochrome oxidase-negative fibers 6. The antibodies are also found in juvenile myositis (27% prevalence) where they associate with more severe disease, greater pulmonary symptoms, and increased hospitalizations 7. Anti-NT5C1A autoantibodies can be produced locally within muscle tissue, suggesting their involvement in disease pathogenesis 8.