Clinical History:
This 40-year-old patient presented with a one-year history of slowly progressive painful burning sensation involving both feet. Electrodiagnostic studies (NCS) were normal (i.e. negative for evidence of large fiber neuropathy). Skin biopsies from the ankle, knee and thigh were performed to evaluate for possible small fiber neuropathy.
Question:
What abnormality is seen in the Figure #1 from a PGP9.5 immunostained tissue section?
A. Beaded fibers
B. Melanocyte staining
C. Subepidermal plexus
D. No abnormality
Figure 1: PGP9.5 immunostained frozen section (600x original magnification)
Answer:
What abnormality is seen in Figure #1 from a PGP9.5 immunostained tissue section?
A. Beaded fibers <– correct answer
This high magnification image show several intraepidermal nerve twigs (see arrows) which have crossed the subepidermal basement membrane into the epidermis. Note that many of these have a “beaded” appearance.
The intraepidermal nerve fibers have an abnormal beaded appearance. This is felt to reflect the presence of nerve fiber injury, and is similar to axonal spheroids seen in the brain due to axonal injury with associated impairment of axonal transport and patchy accumulation of neurofilament (colloquially designated a “constipated axon”).
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