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Patient with Ptosis and Weakness

Jon Wilson, MD neuropathologist at arkana laboratories
By Jon Wilson, MD

Oct 16, 2023

Figure 1: Hematoxylin and eosin stained frozen section

Clinical history

This 60-year-old patient presented with chronic ptosis and mild muscle weakness.  CPK levels were within normal limits.

 

Based on Figures #1 – #4 which of the following is the best diagnosis?

A. Polymyositis

B. IBM

C. Mitochondrial myopathy

D. McArdle disease

 

Figure 1: This medium power image shows scattered muscle fibers with mild basophilic tinctoral quality.

Figure 2: A higher power image shows scattered muscle fibers with coarse bright magenta to bluish staining between the sarcomeres and in a subsarcolemmal distribution (ragged-red muscle fibers).

Figure 3: This medium power image shows frequent COX-negative myofibers (blue tinctoral quality with this dual stain preparation)

Figure 4: Electron microscopy shows frequent muscle fibers with mitochondrial abnormalities:

-enlarged

-spirally arranged critae

-paracrystalline inclusions (“parking lot inclusions”)

 

Correct answer: C. Mitochondrial myopathy

 

 

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