What is the role of anti-striated muscle (anti-SM) ab in the evaluation of myasthenia gravis (MG)?

Updated: Aug 27, 2018
  • Author: Abbas Jowkar, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

The anti–striated muscle (anti-SM) Ab refers to a class of antibodies against components of skeletal muscle including titin, the ryanodine receptor, myosin, and alpha-actin. Anti-SM Ab is present in about 70–80%of patients with thymoma and MG who are younger than 40 years, and 30% of adult patients with MG without thymoma and 24% of patients with thymoma without MG. [45] Thus, a positive test result should prompt a search for thymoma in patients younger than 40 years. In individuals older than 40 years, anti-SM Ab can be present without thymoma. Unlike AChR antibodies, striational antibodies can be of value in monitoring the disease course. Persistence or recurrence of high titers of these antibodies may indicate incomplete resection or recurrence of thymoma, respectively.


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