Clinical History:
This 66-year old patient presented with clinical features of mononeuropathy.
Sural nerve biopsy showed features of a chronic active axonopathic process. While there was significant loss of large diameter myelinated axons, there was greater loss of small diameter myelinated and unmyelinated axons.
What is your diagnosis?
Figures: Toluidine blue stained thick section, Congo Red and Thioflavin
Correct Answer:
The toluidine blue stained thick section shows features of an axonopathic process which involves small myelinated axons to a greater degree than large myelinated axons. Congo red and Thioflavin stain preparations highlight the presence of amyloid adjacent to small endoneurial blood vessels.
These features are consistent with involvement of peripheral nerve by amyloidosis (so-called amyloid neuropathy) which may show preferential loss of small myelinated and unmyelinated axons.
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