CMT 1A: Nonmyelinating Schwann cell involvement with well-preserved unmyelinated

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J Neuropathol Exp Neurol. 2007 Nov;66(11):1027-36.

Nonmyelinating Schwann cell involvement with well-preserved

unmyelinated axons in Charcot-Marie-Tooth disease type 1A.

Koike H, Iijima M, Mori K, Yamamoto M, Hattori N, Katsuno M, Tanaka

F, Watanabe H, Doyu M, Yoshikawa H, Sobue G.

Department of Neurology, Nagoya University Graduate School of

Medicine, Nagoya, Japan.

Electron microscopic examination was performed to compare

morphologic changes of nonmyelinating Schwann cells and unmyelinated

axons in patients with Charcot-Marie-Tooth disease type 1A (CMT1A)

with peripheral myelin protein 22 duplication (n = 27) and normal

control individuals (n = 14).

Complete transverse sural nerve cross-sections were obtained in 16

patients and the total number of axons and Schwann cells in each

cross-section was estimated.

In patients with CMT1A, the number of myelinated axons was

significantly decreased, whereas unmyelinated axons were well-

preserved and did not show any marked changes. The numbers of

nuclei, subunits, and profiles of nonmyelinating Schwann cells were

all increased significantly in patients with CMT1A, whereas the

numbers of axons per unmyelinated axon-containing subunit were

significantly decreased.

Schwann cell subunits consisted of layers of flattened cytoplasmic

profiles wrapped around unmyelinated axons in the patient with

CMT1A. The numbers of nonmyelinating Schwann cell profiles were

increased and the numbers of axons per unmyelinated axon-containing

subunit were reduced even in young patients with well-preserved

myelinated fibers.

In conclusion, there is marked alteration of the population and

morphology of nonmyelinating Schwann cells, and axon-Schwann cell

interactions seem to be regulated differently between myelinated and

unmyelinated fibers in CMT1A.