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Background and aims: We report on an 18-year-old male
patient with clinical and electrophysiological signs of
demyelinating CMT. However, nerve ultrasound did not
reveal the typical finding of homogenous swelling of
peripheral nerves, but a rather slight general swelling with
additional focal nerve swelling distant from entrapment
sites. This finding led to differential diagnoses like
congenital chronic inflammatory demyelinating
polyneuropathy (CIDP). Finally, more extensive genetic
testing revealed a mutation in the SHT3TC2 gene (CMT
4C).
Methods: Clinical and electrophysiological examinations,
nerve ultrasound and genetic testing.
Results: The patient with negative family history developed
progressive sensory symptoms, weakness and skeletal
deformities since early childhood. He was wheelchairbound
since the age of 16. Electrophysiological testing
revealed extreme slowing of conduction velocities (4–10
m/s) and prolonged distal motor latencies of peripheral
nerves as well as reduced amplitudes of compound muscle
action potentials (CMAPs). Nerve ultrasound showed focal
swelling in many nerves distant from typical entrapment
sites. The cross-sectional area (CSA) in swelling sites
ranged from 13.6mm2 (ulnar nerve) and 23.5mm2 (median
nerve) to 42.3mm2 (fibular nerve). Genetic testing of
PMP22, MPZ and Cx32 genes was unremarkable. Later on,
genetic testing revealed two compound heterozygote
mutations of the gene SH3TC2 as cause of CMT 4C.
Conclusion: This case highlights nerve ultrasound findings
in a patient with CMT 4C. Our results differ from published
findings in other demyelinating CMT subforms. Further
research is needed to determine the value of nerve
ultrasound in the differential diagnosis of CMT subforms or
against other polyneuropathies like CIDP.