5/15/2007 Case 1: Myofibrillary myopathy with desmin accumulation

Clinical History:

A 48 year old woman with a questionable history of muscle weakness of 1-2 years duration rapidly developed progressive weakness of both proximal and distal muscles, more in the lower extremities than in the upper extremities. Neurological examination showe~ 4/5 strength in the hip girdle muscles and bilateral foot drop, worse on the left. CK was reported as normal. EMG showed minimal neuropathic changes. The patient was transferred to University Hospital in Newark and a biopsy was obtained from the left gastrocnemius.

Diagnostic Notes:

The submitted slide was a cryostat section of snap-frozen muscle stained with H&E. (Thanks again to Dr Sharer's technician for producing so many cryostat section recuts.) The biopsy showed muscle with retained architecture, but with some prominently vacuolated fibers. There were rare rimmed vacuoles, most vacuoles just were empty. There were rare fibers with internalized nuclei, some with dark cytoplasmic inclusions, and some fibers with a necrotic hypereosinophilic appearance (note that the CPK 'was not elevated). Some fibers were small.

Dr Sharer found only rare CD68-positive macrophages. The margins of some vacuoles were immunopositive for alpha-B crystallin, and the dark inclusions were desmin-positive. His final diagnosis was one of Myofibrillary Myopathy with Desmin Accumulation ("Desminopathy").

Slide Image:

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