Charcot-Marie-Tooth disease type 1B

What it is

Charcot-Marie-Tooth disease type 1B (CMT1B) is a form of CMT1, caused by mutations in the MPZ gene (1q22), that presents with the manifestations of peripheral neuropathy (distal muscle weakness and atrophy, foot deformities and sensory loss). The phenotype is variable depending on the particular mutation. Two distinct presentations have been described: (1) an early infantile onset severe phenotype with delayed walking and motor nerve conduction velocities (MNCV) age 40), with normal or mildly slowed MNCV and more frequent hearing loss and pupillary abnormalities. CMT1B can also cause the classical CMT phenotype in about 15% of total CMT1B cases.

Key facts

Prevalence

1-9 / 100 000

Age of onset

Adolescent, Adult, Childhood, Infancy

Inheritance

Autosomal dominant

Classified as

Disease

Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.

Signs and symptoms

These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.

Gene

ICD-10 codes

ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.

Related health topics

Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.

Cross-references