1. Case Study 83 Leonidas Arvanitis, MD

2. Question 1:
The patient is a 50-year-old female with AIDS complaining of a 3 month history of muscle weakness
Laboratory studies showed a normal EMG and CK levels
Describe the findings on an open biopsy of the left quadriceps muscle:
Click here to view frozen section H&E slide

3. Answer 1: Abnormal variation in myofiber sizes (10-100 microns)
Clustered and scattered angulated atrophic fibers
No excess of internalized nuclei
Occasional nuclear clumps
No degenerating or regenerating fibers
No inflammatory infiltrates

4. Question 2:
What is the most significant histologic finding seen in this biopsy specimen?

5. Answer 2: Abnormal variation in myofiber sizes (10-100 microns)
Clustered and scattered angulated atrophic fibers
No excess of internalized nuclei
Occasional nuclear clumps
No degenerating or regenerating fibers
No inflammatory infiltrates

6. Question 3:
How does the pattern of fiber atrophy help us determine the cause for the atrophy?

7. Answer 3: Changes random and diffuse
Myopathy/dystrophy
Presence of small angulated fibers
Suggests denervation
Presence of small group atrophy
Denervation
Presence of large group atrophy
Presence of perifascicular atrophy
Dermatomyositis

8. Question 4:
In our case the atrophy is random and diffuse suggestive of a myopathy or dystrophy
What histochemical stain would be most helpful in further defining the specific muscle types involved?

9. Answer 4:
ATPase 9.4
ATPase 4.6
Click here to view an ATPase 9.4 stain of a normal muscle biopsy
Click here to view an ATPase 4.6 stain of a normal muscle biopsy

10. Question 5:
What is the normal staining pattern of muscle fibers on ATPase 9.4 and 4.6 respectively?

11. Answer 5: Muscle fiber type 1 2A 2B 2C ATPase 9.4 + +++ ATPase 4.6 -
-, +, ++, +++ represent increasing intensity of stain

12. Question 6: What is the staining pattern of ATPase stains in our case?
Click here to view ATPase 9.4 stain
Click here to view ATPase 4.6 stain

13. Answer 6:
The atrophic muscle fibers are almost exclusively of the type 2 subtype

14. Question 7:
What additional clinical information would be useful to better define the disease process?

15. Answer 7: History of alcohol abuse Medication history
Other associated comorbidities
In our case the patient was treated with corticosteroids

16. Question 8:
What are the causes of type 2 myofiber atrophy?

17. Answer 8: Alcohol use Steroids Disuse Endocrinopathies
Connective tissue disorders

18. Question 9:
Which subtype of type 2 myofibers are particularly affected?

19. Answer 9:
Type 2B fibers

20. Question 10:
What is your final diagnosis?

21. Answer 10:
Type 2 myofiber atrophy due to corticosteroid use