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Weakness and Atrophy

By Joshua Sonnen, MD

Jul 14, 2023

Clinical History

This 75-year-old man with amyotrophic lateral sclerosis (ALS) for 5 years has a past medical history of gout and dysphagia. Upon physical exam, he showed slowly progressive weakness: Left>right, upper>lower extremity, distal>proximal, and grip strength 2/5 left, 4/5 right.


What is the most likely diagnosis?

A. Denervation
B. Myotonic dystrophy
D. Gouty tophus


The answer is C. sIBM.

Sporadic Inclusion Body Myositis (sIBM)

Resembles other idiopathic inflammatory myopathies. Rimmed vacuoles (inclusion bodies) may not be identified on H&E or trichrome.

  • Immunohistochemistry: abnormal protein aggregates (e.g. TDP-43, p62, LC3B) in inclusions
  • Granular dense material in vacuoles on Toluidine blue stained, plastic embedded, 1-micron-thick section
  • Mitochondrial pathology: COX-/SDH+ (ragged-red equivalent) fibers in most cases

Treatment resistant, progressive, asymmetric distal weakness mimics ALS Finger flexor (grip strength) weakness is characteristic.


Quick note: This post is to be used for informational purposes only and does not constitute medical or health advice. Each person should consult their own doctor with respect to matters referenced. Arkana Laboratories assumes no liability for actions taken in reliance upon the information contained herein.