What is the role of muscle biopsy in the workup of sporadic inclusion body myositis (s-IBM)?

Updated: Jun 08, 2018
  • Author: Michael P Collins, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Muscle biopsy is the criterion standard for ascertaining the diagnosis of s-IBM.

  • Selection of muscle to be biopsied

    • Findings may be patchy. Therefore, care must be taken in the preparation and examination of sufficient tissue to avoid sampling error.

    • The biopsy sample should be taken from a muscle that is affected moderately (ie, Medical Research Council grade 4 to 4 minus), yet one that is conventionally examined (eg, quadriceps, deltoid, biceps brachii). A severely atrophied, "end-stage" muscle should be avoided.

    • Beyond establishing electrodiagnostic evidence for a myopathic process, the needle electrode examination may be used to determine which muscle would be optimal for biopsy based on electrodiagnostic findings. However, the biopsy sample should not be taken directly from the site of the needle electrode insertion to avoid artifact directly related to changes in the muscle due to insertion of the needle electrode.

    • Polyneuropathy may be present in a number of cases; thus, the sampling of distal muscles should be avoided. Nerve biopsy generally is not indicated in the evaluation of s-IBM.

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