Type 1B Research - from Costa Rica

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Abstract from Neurogenetics. 2003 Jul 5

Charcot-Marie-Tooth disease: a novel Tyr145Ser mutation in the myelin

protein zero ( MPZ, P0) gene causes different phenotypes in homozygous

and heterozygous carriers within one family.

Leal A, Berghoff C, Berghoff M, Del Valle G, Contreras C, Montoya O,

E, Barrantes R, Schlotzer-Schrehardt U, Neundorfer B, Reis A,

Rautenstrauss B, Heuss D.

Institute of Health Research (INISA) and School of Biology, University

of Costa Rica, San , Costa Rica.

Charcot-Marie-Tooth disease type 1B (CMT 1B) is caused by mutations in

the gene coding for peripheral myelin protein zero (MPZ, P0) that plays

a fundamental role in adhesion and compaction of peripheral myelin.

neuropathy due to a novel Tyr145Ser MPZ mutation. Four family members

were heterozygously affected; two siblings of two heterozygous

carriers were homozygous for this mutation. On neurological examination

the heterozygous parents and their homozygous children both showed

distal sensory deficits. The mother and the siblings displayed impaired

deep tendon reflexes and mild sensory ataxia. The homozygous individuals

were more severely affected with an earlier age of onset, distal motor

weakness, and pupillary abnormalities. Electrophysiological

studies revealed both signs of demyelination and axonal nerve

degeneration. The sural nerve biopsy of one sibling showed thinly

myelinated nerve fibers, onion bulb formation, and clusters of

regenerating fibers. On electron microscopy axonal degeneration and

decompaction of inner myelin layers were found. This Costa Rican family

heterozygous state of the Tyr145Ser mutation carriers.