muscle biopsy

Indications: 1) generalized disorder with multiorgan system involvement (muscle is easily accessible tissue) a) sarcoidosis b) vasculitis 2) primary neuromuscular disease Contraindications: Caution: 1) muscle pathology is frequently multifocal & not diffuse 2) biopsy of uninvolved area of muscle may not show pathology Procedure: 1) frozen sections necessary 2) formalin fixation destroys muscle fiber architecture & inactivates enzymatic activity useful for diagnosis 3) electron microscopy for ultrastructure Interpretation: Features of interest: 1) changes in fiber size & shape 2) abnormalities in distribution of fiber type 3) changes is sarcolemmal nuclei 4) degeneration & regeneration of muscle fibers 5) inflammatory infiltrates

References

Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998