CMT 1B: Rare myelin protein zero sequence variant in late onset

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J Neurol Sci. 2007 Dec 15;263(1-2):177-9.

Rare myelin protein zero sequence variant in late onset CMT1B.

Souayah N, Seltzer WK, Brannagan TH, Chin RL, Sander HW.

Department of Neurology, Department, New Jersey Medical School, 90

Bergen Street DOC 8128, Newark, NJ 071011, USA.

Myelin protein zero (MPZ) mutations cause demyelinating neuropathies

that range from severe neonatal to milder adult forms. We report a 65-

year-old woman with slowly progressive leg weakness starting at 47.

Examination revealed distal weakness and atrophy in all extremities,

impaired light touch in both feet and pin perception to proximal

calves, absent leg reflexes, and unsteady gait.

Electrodiagnostic studies revealed a severe sensorimotor

polyneuropathy with conduction velocities of 25 m/s - to normal. The

conduction velocities in the upper 20's were seen in lower

extremities with severe reduction of the corresponding compound

muscle action potential amplitudes. She had a MPZ mutation with A-C

transversion (nucleotide: 116, codon: 10, histidine-to-proline). Her

sister has an identical mutation, with high arches, distal leg

weakness, decreased vibration sensation in toes and ankle areflexia.

Nerve conduction studies revealed a moderate-severe sensorimotor

polyneuropathy with nerve conduction velocities of 36 m/s - to

normal. Their mother had an abnormal gait and conduction velocities

of 29-30 m/s. A third sister is clinically and genetically

unaffected. One report has previously described four patients with

this mutation with similar clinical and electrodiagnostic features.

In patients tested for possible CMT, the frequency of MPZ His-Pro

codon 10 substitutions was 0.11% (27 of 24,076 alleles).