Case Study 83 Leonidas Arvanitis, MD

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

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

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

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

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

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

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?

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

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

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

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

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

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

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

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

Answer 8: Alcohol use Steroids Disuse Endocrinopathies Connective tissue disorders

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

Answer 9: Type 2B fibers

Question 10: What is your final diagnosis?

Answer 10: Type 2 myofiber atrophy due to corticosteroid use