1. Case Study 85 Leonidas Arvanitis

2. Question 1:
A 25 year old female complains of hypotonia and muscle weakness
CK levels are mildly elevated
Describe the histologic findings on the H&E and Gomori trichrome stains
Click here to view H&E and Gomori stains

3. Answer 1: H&E stained frozen sections
Abnormal variation in myofiber sizes (15-80 microns)
Mild excess of internalized nuclei
Gomori trichrome reacted sections
Dark staining inclusions which are cytoplasmic and clustered at the periphery of the fibers

4. Question 2:
Based on the most likely diagnosis what would electron microscopy show?

5. Answer 2:
Electron dense rods or ovoid structures derived from Z-line material

6. Question 3:
What is the major constituent of theses rods?

7. Answer 3:
A-actinin

8. Question 4:
What is your diagnosis?

9. Answer 4:
Nemaline myopathy

10. Question 5:
Nemaline myopathy is caused by mutations in which genes?

11. Answer 5: The most common mutations involve the ACTA1 and NEB genes
ACTA1 gene encodes skeletal muscle α-actin
NEB gene encodes nebulin

12. Question 6:
Are rods specific to nemaline myopathy?

13. Answer 6: No, they can also be seen in Myotendinous junctions
External ocular muscles
Aging muscles