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]

Note: Acronym HMN is also used interchangeably with DHMN.

• Motor neuron disease
• Hereditary motor and sensory neuropathies
• Spinal muscular atrophies
• Charcot–Marie–Tooth disease
• Hereditary spastic paraplegia