Basic Neuroscience · Neuropathology
Muscle Pathology
Muscle biopsy findings across the inflammatory myopathies, dystrophies, and congenital myopathies. The downloadable PDF includes the corresponding stained histology slides.
Classification
| Category | Diseases |
|---|---|
| Inflammatory myositis | Polymyositis · Dermatomyositis · Inclusion body myositis (IBM) |
| Myopathy | Duchenne · Myotonia · Congenital (central core, myotubular/centronuclear, nemaline rod) · Mitochondrial · Metabolic |
Biopsy findings
| Disease | Pathological findings |
|---|---|
| Polymyositis | Endomysial mononuclear infiltrates (between and around individual myofibers); fiber-type grouping; type II atrophy. Lymphocytes invade the muscle myofiber. |
| Dermatomyositis | Perifascicular infiltration and atrophy (at the periphery of fascicles). A vasculitis involving endomysial capillaries and arterioles. |
| Inclusion body myositis | Hallmark "rimmed vacuoles" in the muscle fibers lined with an eosinophilic rim. Affected myofibers have vacuoles containing basophilic granules — myelinoid membranous bodies and small chunks of amyloid similar to the neurofibrillary tangles of Alzheimer's disease. |
| Duchenne dystrophy | Muscle-fiber degeneration (rounded, variable size); increased fat and connective tissue. |
| Myotonic dystrophy | More internal nuclei than any other muscle disorder; on longitudinal section the internal nuclei tend to line up; increased connective tissue. |
| Central core myopathy | Pale central core in nearly every type I muscle fiber (results from absence of mitochondria); shown on NADH histochemical stain. |
| Myotubular / centronuclear myopathy | Centrally located nuclei with perinuclear halos (clear surrounding zone from absence of myofibrils). Differs from myotonic dystrophy in having only a single internal nucleus per fiber. |
| Nemaline rod myopathy | Trichrome stain shows dark fibrillar material (nemaline rods) within the muscle fiber. |
| Mitochondrial myopathy | Trichrome stain shows subsarcolemmal accumulations of "ragged red fibers." The red color is due to large numbers of abnormal mitochondria representing a compensatory proliferation. |
| Denervation atrophy | Small angular fibers; fiber-type grouping followed by group atrophy. |
LIGHTS on RITE by Ahmed Koriesh