Anti–Cytosolic 5′‐Nucleotidase 1A Autoantibodies Are Absent in Juvenile Dermatomyositis

OBJECTIVE: To assess anti–cytosolic 5′‐nucleotidase 1A (anti–cN‐1A) autoantibodies in children with juvenile dermatomyositis (DM) and healthy controls, using 3 different methods of antibody detection, as well as verification of the results in an independent cohort. METHODS: Anti–cN‐1A reactivity was assessed in 34 Dutch juvenile DM patients and 20 healthy juvenile controls using the following methods: a commercially available full‐length cN‐1A enzyme‐linked immunosorbent assay (ELISA), a synthetic peptide ELISA, and immunoblotting with a lysate from cN‐1A–expressing HEK 293 cells. Sera from juvenile DM patients with active disease and those with disease in remission were analyzed. An independent British cohort of 110 juvenile DM patients and 43 healthy juvenile controls was assessed using an in‐house full‐length cN‐1A ELISA. RESULTS: Anti–cN‐1A reactivity was not present in sera from juvenile DM patients or healthy controls when tested with the commercially available full‐length cN‐1A ELISA or by immunoblotting, in either active disease or disease in remission. Additionally, in the British juvenile DM cohort, anti–cN‐1A reactivity was not detected. Three Dutch juvenile DM patients had weakly positive results for 1 of 3 synthetic cN‐1A peptides measured by ELISA. CONCLUSION: Juvenile DM patients and young healthy individuals did not show anti–cN‐1A reactivity as assessed by different antibody detection techniques.