Anti-Skeletal Muscle Antibody

Alternative name: Muscle Skeletal (Striated) Antibodies
Description: Found in patients with Myasthenia Gravis usually in the presence of Anti-acetylcholine receptor antibodies are far more characteristic. The presence of striated muscle antibodies in myasthenia suggests the presence of thymoma. IgM anti striated muscle antibodies may also occur in some patients with nuclear hepatitis, acute viral infections and polymyositis. Low titres may occur in viral infections notably EBV and infectious hepatitis.
Indication: Test is of limited value, anti-acetylcholine receptor antibody being the test of choice for myasthenia. Main indication is myastenia associated with thymoma.
Interpretation: Anti-striated muscle antibodies are are found in 25-40% of patients with Myasthenia Gravis but primarily those with thymoma. Absence of anti-skeletal muscle antibodies is strong evidence against the presence of thymoma except in a small group of young myasthenics, usually male. Presence of these autoantibodies predicts the risk of myasthenia in patients with thymoma and reoccurance of thymoma after surgery.
Sample: Serum Separator Tube (SST)
Assay details: Indirect immunfluorescence primate tissue (striated muscle)
Restrictions: Referred test
Reference range: Negative/positive
Assay Range Notes:
Turnaround time: 28 days
Analysing laboratory: Sheffield PRU