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Antibodies to smooth muscle in blood
Last reviewed: 05.07.2025
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Normally, antibodies to smooth muscles are absent in the blood serum.
Smooth muscle antibodies (SMAs) are antibodies to the protein actin or non-actin components (tubulin, vimentin, desmelin, and skeletin) and are produced in response to hepatocyte injury. Smooth muscle antibodies are detected by indirect immunofluorescence.
Smooth muscle antibodies are detected in 60-80% of cases of autoimmune (lipoid) hepatitis (in titer 1:80 and higher), in 50% of cases of primary biliary cirrhosis and are not detected in systemic lupus erythematosus and lesions of the extrahepatic bile ducts. Smooth muscle antibodies are present in 70% of patients with chronic active hepatitis and belong to the IgG class.
Smooth muscle antibodies are found in acute viral hepatitis, and disappear during recovery from the latter. In some cases, smooth muscle antibodies can be found in low titers in infectious mononucleosis, CMV infection, mycoplasma pneumonia, lymphoproliferative diseases, drug addiction, in women suffering from infertility, malignant neoplasms, and sometimes in healthy people. In these groups of patients, smooth muscle antibodies belong to the IgM class.
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