This adult patient presented with progressive muscle weakness, elevated CK, and was admitted for rhabdomyolysis. Skeletal muscle biopsy was performed of the quadriceps (Image 1, Hematoxylin and eosin-stained frozen section, original magnification x200). What is your diagnosis?

 

Answer:  Lipid Storage Myopathy

Optically clear spaces within muscle may be due to lipid or glycogen.  Optically clear spaces may also occur due to ice crystal formation when muscle biopsy tissue is frozen too slowly or is edematous (so-called “freezing artifact”).  In this case, the vacuoles are due to abnormal accumulation of lipid (i.e. Lipid Storage Myopathy), see Image 2.  (Figure 2:  Oil-red-O stained frozen section, original magnification x200).