Hematoxylin and eosin (H&E) stained frozen sections of the paraspinal muscle biosy revealed mild variation in myofiber sizes with occasional atrophic fibers, rare nuclear clumps, and an excess of internalized nuclei. No degenerating or regenerating fibers were seen. There were numerous fibers that contained subsarcolemmal and occasional central vacuoles. These vacuoles (blebs) frequently contained PAS positive material (low power, and high power ). This material was completely digested with diastase. There was mild acid phosphatase reactivity in some of the vacuoles, but most of the vacuoles did not stain with acid phosphatase. The NADH-TR reaction revealed rare small dark fibers and vacuoles. The ATPase reactions (9.4 and 4.3) revealed a checkerboard pattern with occasional atrophic type II fibers. The subsarcolemmal vacuoles occurred in both type I and type II fibers. There was a 2:1 type I to type II fiber ratio. No ragged red fibers were seen (Gomori trichrome). Electron microscopy revealed subsarcolemmal deposits of non-membrane bound glycogen. There were small focal regions of increased free glycogen within myofibers as well.
We also reviewed the previously obtained limb muscle specimen and noted fibers with subsarcolemmal vacuoles that were much less apparent than in the paraspinal muscle specimen. There was only minimal staining of the contents of the vacuoles with PAS.
What additional studies (enzyme histochemistry or biochemical activity assays) need to be done in order to establish a diagnosis in this case?
DIAGNOSIS & DISCUSSION