dHMN-1

2007

What Is dHMN-1?

dHMN-1 is a type of CMT with an established locus but no confirmed causative gene identified to date.

For dHMN-1, genetic evidence supports an autosomal dominant inheritance pattern, meaning that just one of the gene’s two copies needs a mutation to cause this subtype.

Clinical Features

The age of symptom onset in dHMN-1 is variable, ranging from childhood to adulthood. Symptoms typically begin in the lower extremities and progress over time to involve the upper limbs. Nerve conduction studies usually show somewhat slowed conduction velocities and reduced amplitudes, consistent with an axonal form of CMT.

dHMN-1 symptoms may include:

  • Weakness in the feet and lower legs
  • Muscle atrophy
  • Foot drop
  • Reduced or absent reflexes
  • Reduced sensation
  • A steppage-style walking pattern
  • Foot deformities, including high arches, and hammertoes (clawed toes)
  • Progressive involvement of the hands and forearms
  • Difficulty with fine motor skills and manual dexterity
  • Additional symptoms not listed here

Disease Course

dHMN-1 shows wide variability in severity and progression. Some individuals are mildly affected, while others develop a more severe disease. Disease progression is generally slow, and life expectancy is not reduced.

Clinical Basics

Subtype
dHMN-1

Classification
dHMN/HMN

Neuropathy Type
Axonal

Inheritance Pattern
autosomal dominant

Genetic Context

HGNC-Approved Gene Symbol
Gene is Unknown at This Time

Chromosome
7q34-q36

Zygosity of Responsible Variant
Heterozygous

Variant Mechanism

Unknown

Details

Mechanistic basis:
Gene unknown

Confidence:
High

Prediction:
Harding's classification defined dHMN-1 by juvenile onset and dominant transmission of distal motor weakness without sensory loss, criteria that group families rather than identify a locus. No gene has been definitively established for the type and no linkage interval fixes it, leaving not even a candidate genomic address from which the literature could reason toward a mechanism.

Rationale:
Clinical criteria assembled this type, and clinical criteria cannot yield a molecular lesion. Distal motor neuropathy genes found since, acting through varied mechanisms, carry their own designations, so dHMN-1 has neither a protein nor an allele class whose behavior could be predicted.

dHMN-1 OMIM Entry

dHMN-1 OMIM

More Info

dHMN-1 Research Opportunity

CMT Natural History Study

Original Discovery Publication

Publication Title

A Novel Locus for Distal Motor Neuron Degeneration Maps to Chromosome 7q34-q36

Authors

Gopinath, S., Blair, I. P., Kennerson, M. L., Durnall, J. C., & Nicholson, G. A.

Publication Date
March 13, 2007

DOI
10.1007/s00439-007-0348-9

Updated: July 18, 2026 | By: K. Raymond

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