Hereditary neuropathies affect the peripheral nerves, causing subtle symptoms that worsen gradually.
(See also Overview of the Peripheral Nervous System.)
Hereditary neuropathies may affect only
- Motor nerves (motor neuropathies)
- Sensory and autonomic nerves (sensory neuropathies)
- Sensory and motor nerves (sensory and motor neuropathies)
Motor nerves control muscle movement, and sensory nerves carry sensory information—about such things as pain, temperature, and vibration—to the brain. Autonomic nerves regulate involuntary body process.
Some hereditary neuropathies are relatively common but often are not recognized.
The genes responsible for many hereditary neuropathies have been identified. These neuropathies include
- Some forms of Charcot-Marie-Tooth disease
- Refsum disease
- Fabry disease
- Hereditary neuropathy with liability to pressure palsies
When the sensory nerves are affected, the ability to feel pain and changes in temperature may be impaired more than the ability to sense vibration and position (knowing where the arms and legs are). The hands and feet are affected most. Because people cannot feel pain, they may injure their feet and not know it. Such injuries increase the risk of infections, including bone infections, and risk of joint damage (called neurogenic arthropathy, or Charcot joints). If the ability to sense vibration and position is affected, people have problems with balance and walking.
When motor nerves are affected, muscles weaken, waste away (atrophy), and can become completely paralyzed.
When autonomic nerves are affected, body processes do not function normally. For example, blood pressure may decrease when a person stands (called orthostatic hypotension), making the person feel dizzy or light-headed. Men may have difficulty initiating and maintaining an erection (erectile dysfunction). People may involuntarily pass urine (urinary incontinence) or have difficulty emptying the bladder (urine retention). Some people are severely constipated.