Distal hereditary motor neuronopathies (distal HMN, dHMN), sometimes also called distal hereditary motor neuropathies, are a genetically and clinically heterogeneous group of motor neuron diseases that result from genetic mutations in various genes and are characterized by degeneration and loss of motor neuron cells in the anterior horn of the spinal cord and subsequent muscle atrophy.[citation needed]
Although they can hardly be distinguished from hereditary motor and sensory neuropathies on the clinical level, dHMNs are considered a separate class of disorders.[citation needed]
Another common system of classification groups many of DHMNs under the heading of spinal muscular atrophies.[citation needed]
In 1993, A. E. Hardnig proposed to classify hereditary motor neuropathies into seven groups based on age at onset, mode of inheritance, and presence of additional features. This initial classification has since been widely adopted and expanded and currently looks as follows:[1][2]
| Type | OMIM | Gene | Locus | Inheritance | Common names and characteristics |
|---|---|---|---|---|---|
| DHMN1 | 182960 | ? | 7q34–q36 | Autosomal dominant | Autosomal dominant juvenile distal spinal muscular atrophy
|
| DHMN2A | 158590 | HSPB8 | 12q24.23 | Autosomal dominant | Autosomal dominant distal spinal muscular atrophy
|
| DHMN2B | 608634 | HSPB1 | 7q11.23 | Autosomal dominant | Adult onset |
| DHMN2C | 613376 | HSPB3 | 5q11.2 | Autosomal dominant | |
| DHMN2D | 615575 | FBXO38 | 5q32 | Autosomal dominant | Distal spinal muscular atrophy with calf predominance
|
| DHMN3 DHMN4 |
607088 | ? | 11q13 | Autosomal recessive | Distal spinal muscular atrophy type 3
|
| DHMN5A | 600794 | GARS | 7p14.3 | Autosomal dominant | Distal spinal muscular atrophy type VA |
| DHMN5B | 614751 | REEP1 | 2p11.2 | Autosomal dominant | Distal spinal muscular atrophy type VB
|
| DHMN6 | 604320 | IGHMBP2 | 11q13.3 | Autosomal recessive | Distal spinal muscular atrophy type 1 (DSMA1); spinal muscular atrophy with respiratory distress type 1 (SMARD1)
|
| DHMN7A | 158580 | SLC5A7 | 2q12.3 | Autosomal dominant | Spinal muscular atrophy with vocal cord paralysis; Harper–Young myopathy
|
| DHMN7B | 607641 | DCTN1 | 2p13.1 | Autosomal dominant | Adult onset with vocal cord paralysis and facial weakness |
| DHMN8 | 600175 | TRPV4 | 12q24.11 | Autosomal dominant | Congenital distal spinal muscular atrophy
|
| DHMNJ | 605726 | SIGMAR1 | 9p13.3 | Autosomal recessive | Distal spinal muscular atrophy type 2; Jerash type spinal muscular atrophy
|
Note: Acronym HMN is also used interchangeably with DHMN.
|
Diseases relating to the peripheral nervous system
| |||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||
