Reaching an accurate diagnosis is often a long and frustrating process for those with myositis and their doctors. Myositis diseases are rare and complex, with poorly understood origins and features that may be similar to other disorders. As such, there is usually no single lab test that can easily diagnose any of the forms of myositis.
While it is ideal to have reliable diagnostic criteria that are validated by research evidence, at this time scientists are still working to develop diagnostic criteria for most myositis diseases. Until this process is completed, clinicians usually decide on a diagnosis based on clinical signs and symptoms, available clinical tests, and their own knowledge about the what conditions are present in their geographic area.
Classification criteria, which often rely on the same diagnostic tests, are more strict than the broader criteria for diagnosis. Classification criteria must be stricter, because they are used for research studies to assemble a group of participants that are more or less the same. When a study population is homogeneous in this way, the conclusions drawn by the study are more reliable.
Classification criteria, while not intended for diagnosis, may nevertheless be helpful to the clinician. In 2017, an international group of myositis experts created a set of classification criteria for adult and juvenile myositis. These criteria are currently being revised.
Click on the form of myositis below to see guidelines for establishing a specific diagnosis. Before diagnosing any form of myositis, your doctor will need to rule out other similar conditions.
Immune-mediated necrotizing myopathy
(also known as necrotizing myopathy or necrotizing autoimmune myopathy)
Disclaimer: Information provided on this website is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with any questions you may have regarding a medical condition.