What are the pathologic findings characteristic of nemaline myopathy (NEM)?

Updated: Mar 11, 2019
  • Author: Matthew Harmelink, MD; Chief Editor: Amy Kao, MD  more...
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Rods, the pathologic hallmark of nemaline rod myopathy, are only visible on modified Gomori trichrome (GT) stain as dark red/purple structures (see image below).

Nemaline rod myopathy, Gomori trichrome (GT) stain Nemaline rod myopathy, Gomori trichrome (GT) stain. Dark blue structures are seen only with this stain. They contain Z disk material, including alpha-actinin and tropomyosin.

Usually, the rods are sarcolemmal but may be intranuclear.

Derived from the Z-disk, rods are often in continuity with the Z-line. They are composed of primarily α-actinin (the primary component of Z-lines) as well as other Z-line and thin filament proteins, including actin, telethonin, and myotilin. Rods presumably form secondary to contractile protein (especially thin filament) dysfunction.

Rods may be seen in many other diseases including inflammatory myopathies, muscular dystrophies, mitochondrial myopathies, HIV myopathy, chronic renal failure, spinal muscular atrophy, Charcot-Marie-Tooth disease, and monoclonal gammopathy.

Other common pathologic features include type-1 fiber predominance or atrophy.

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