In a recent blog we covered polymysotisis, one of the most common disorders in the category of the idiopathic inflammatory myopathies. This group of disorders is characterized by the effects they have on the body’s skeletal muscles, and associated symptoms and manifestations such as various types of cutaneous rashes.
The two main idiopathic inflammatory myopathies are polymyositis (PM) and dermatomyositis (DM). Since we covered the basics in the previous blog, we will use this opportunity to cover diagnosis in greater detail, because the proper diagnosis and monitoring of the body’s response to treatment is incredibly important when attempting to manage these disorders.
Methods of Diagnosis
There are four main diagnostic markers when it comes to identifying idiopathic inflammatory myopathies:
1. Muscle Enzymes — Levels of enzymes such as creatine kinase (CK), aldolase, lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase are typically monitored, as research has found an increase in one or all of these is an indicator of the myopathies.
2. Antibodies — Specifically, “antinuclear antibodies” are also elevated in individuals with PM/DM, although this is not a primary indicator.
3. Electromyography — Because the myopathies are disorders that affect the skeletal muscles, an electromyogram (EMG) is a useful tool as it helps identify abnormal muscle behavior and responses such as spontaneous or irregular fibrillations (contractions).
4. Muscle Biopsy — This is the most definitive way to identify the presence of PM/DM. The most accurate assessment of a biopsy occurs when one is taken from a muscle that has been identified as weakened due to the speculated presence of PM/DM.
There are many instances and causes of muscle weakness, no all of which are related to this specific set of disorders. If you suspect PM or DM, you should ask your physician about the various diagnosis options.
Sources:
Journal of the American Academy of Physician Assistants – Understanding the Idiopathic Inflammatory Myopathies: http://www.jaapa.com/understanding-the-idiopathic-inflammatory-myopathies/article/128910/
Nature Reviews – Rheumatology: http://www.nature.com/nrrheum/journal/v6/n3/pdf/nrrheum.2010.2.pdf