Table 3.
Muscle histopatology in DM1 and DM2.
| Histopathological findings | DM1 | DM2 |
|---|---|---|
| Fiber size variation | +++ | +++ |
| Internal nuclei | +++ |
+++ more in type 2 fibers |
| Type 1 fiber atrophy | ++ | - |
| Type 2 fiber atrophy | + | ++ |
| Type 2 fiber hypertrophy | - | + |
| Nuclear clump fibers |
+ at advanced stages only |
+++ more in advanced stages |
| Atrophic fibers (diam. ≤ 6μm) |
± type 1 and type 2 fibers at advanced stages only |
+++ type 2 fibers |
| Ring fibers | ++ | + |
| Sarcoplasmic masses | ++ | ± |
| Fibrosis |
+++ at late stages only |
++ at late stages only |
| Fatty replacement |
+++ at late stages only |
++ at late stages only |
+++ present in >75% of biopsies; ++ present in 20-50% of biopsies; + present in 10-24% of biopsies; ± occasionally present; - absent