cN-1A (Mup44) antibodies is a serological biomarker for the inclusion body myositis.
Studies show that antibodies against the cytoplasmic 5' nucleotidase (cN -1A) protein are highly specific (95% specificity) for inclusion body myositis, even though they cannot be demonstrated in all cases (sensitivity around 30%). These antibodies can also be detected in systemic lupus erythematosus, Sjögren's syndrome, and other inflammatory muscle disorders, but usually at low titers. Inclusion body myositis is 2-3 times more common in men than in women and occurs almost exclusively in people over 50 years of age.
