Antibody Assessments – Inflammatory Myopathies

00:00 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.