Clinical History:
This 55-year-old patient presented with symmetrical numbness, tingling and burning sensation involving the bottom of their feet which slowly spread upward to above the ankles. Their past medical history is significant for autoantibody positive Rheumatoid arthritis. Electrodiagnostic studies showed features of a moderately severe sensorimotor axonal neuropathy. Extensive laboratory studies were otherwise negative. Nerve biopsy was performed to evaluate for possible treatable forms of neuropathy.
Images of a Toluidine blue stain thick section, electron microscopy and von Kossa stain are supplied.
What is the electron dense material seen within the perineurium on electron microscopy and highlighted by von Kossa special stain on formalin-fixed paraffin embedded tissue sections (medium and high magnification)?
Answer:
- Microcalcification (micromineralization) within the perineurium
- This is not well-demonstrated on Toluidine-stained thick sections from this case, but is nicely shown on electron microscopy as dense material within the perineurium. The granular material is highlighted with a special stain for calcium (von Kossa).
- This is a nonspecific finding which can be seen in a variety of chronic neuropathies, including diabetic neuropathy, and to lesser degrees as an age-related change.
Reference(s) / Additional Reading:
- King RH, Llewelyn JG, Thomas PK, Gilbey SG, Watkins PJ. Perineurial calcification. Neuropathol Appl Neurobiol. 1988 Mar-Apr;14(2):105-23. doi: 10.1111/j.1365-2990.1988.tb00874.x. PMID: 2840592.
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