Distal hereditary motor neuronopathies (distal HMNs,DHMNs, ordHMNs; sometimes also calleddistal hereditary motor neuropathies) are a genetically and clinically heterogeneous group ofmotor neuron diseases that result from geneticmutations in variousgenes and are characterized by degeneration and loss ofmotor neuron cells in theanterior horn of the spinal cord and subsequent muscleatrophy.^{[citation needed]}

Although they can hardly be distinguished fromhereditary 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 ofspinal 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: AcronymHMN is also used interchangeably withDHMN.

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

• Motor neuron diseases

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