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Antibody testing is critical for all patients that have an inflammatory myopathy. When patients
present with a muscle localization, our first step is to prove that inflammation is present in the
muscle with CK, but CK is nonspecific. And the presence of a specific antibody of a certain
antibody can point us in the direction of a diagnosis and help us differentiate polymyositis,
dermatomyositis, inclusion body myositis, necrotizing myopathy and overlap syndromes. With
polymyositis, we actually don't see many antibodies associated with this syndrome and that's
really the diagnosis of exclusion. If we work through each of the other myopathies and don't
see an antibody, we may be dealing with polymyositis. With overlap myositis, we see
prominent antibodies that are associated with these aminoacyl-tRNA synthetases, translation
of proteins. And the one I want you to remember, the anti-synthetase antibody that I would
like for you to recall is anti-Jo1. This is the most commonly associated though there are many
that you can see here. These patients present with idiopathic myopathy often with some type
of interstitial fibrosis in the lungs and the presence of one of these antibodies. Dermatomyositis
is associated with other antibodies. Anti-Mi-2, TIF1, MDA and NXP2 are more commonly seen
in patients with dermatomyositis. Inclusion body myositis does have inflammation, but the
primary problem is degeneration. So we don't see a lot of circulating antibodies that are
specific for this condition. Necrotizing autoimmune myositis, however, we do see important
antibodies and the two I'd like for you to remember are SRP, signal recognition protein-associated
myositis or myopathy and Anti-HMG-CoA reductase antibody syndrome, which again, we
talked about the statin case.