Muscle Neuropathology
Muscle Neuropathology
What You'll Learn
- To separate neurogenic from myopathic change on muscle biopsy
- The muscular dystrophies and their membrane-protein defects
- The inflammatory myopathies — DM, PM, IBM, and immune-mediated necrotizing myopathy — by their distinct immunopathology
- Metabolic, mitochondrial and congenital myopathies and the histochemical stains that reveal them
The neuropathology view of muscle biopsy. Clinical myopathy workup lives in the Neuromuscular notes; for MELAS, MERRF, KSS and the other mitochondrial syndromes see Mitochondrial Disorders.
What You'll Learn
| Pattern | Histology | Stain clue |
|---|---|---|
| Neurogenic (denervation) | Grouped atrophy, small angular fibers, target fibers; reinnervation → fiber-type grouping | ATPase / NADH shows type grouping; esterase+ angular fibers |
| Myopathic | Rounded fiber-size variation, internal nuclei, split fibers, necrosis/regeneration, endomysial fibrosis & fatty replacement | — |
What You'll Learn
| Dystrophy | Pathology | Defect |
|---|---|---|
| Duchenne / Becker | Necrosis-regeneration, opaque hypercontracted fibers, marked fibrosis/fat; DMD = absent, BMD = reduced/patchy | Dystrophin IHC (X-linked) |
| Limb-girdle (LGMD) | Dystrophic pattern; sarcoglycan/dysferlin/calpain loss on IHC/immunoblot | Sarcoglycans, dysferlin, etc. |
| Myotonic dystrophy | Central nuclei (chains), ring fibers, sarcoplasmic masses, type 1 fiber atrophy | DMPK CTG (DM1) |
| FSHD | Myopathic + scattered inflammation | D4Z4 contraction (chr 4q35) |
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