Figure 1.

Muscle histopathology. (A) Minimal changes. Internal nuclei are infrequent. Rare fibers have floccular sarcoplasm or are swollen with hypereosinophilic sarcoplasm. Fiber lysis or regeneration is infrequent. Neither cellular infiltrates nor fibrosis or edema are present. (B) Mild to moderate lesions. Many fibers have a few internal nuclei. A few fibers have floccular sarcoplasm or swelling with hypereosinophilic sarcoplasm. Scattered fibers show lysis or regeneration. There is mild interstitial edema. Neither cellular infiltrates nor fibrosis are present. (C) Moderate to severe lesions. Moderate fibrosis and edema and small foci of leukocytes expand the endomysium. Most fibers have multiple internal nuclei. Some fibers have floccular sarcoplasm or are swollen with hypereosinophilic, occasionally fragmented sarcoplasm. Occasional fibers show lysis or regeneration. Hematoxylin and eosin. 400×.