Five different clinical entities have been described under hereditary sensory and autonomic neuropathies – all characterized by progressive loss of function that predominantly affects the peripheral sensory nerves. Their incidence has been estimated to be about 1 in 25,000.

Hereditary sensory and autonomic neuropathy (HSAN) or hereditary sensory neuropathy (HSN) is a condition used to describe any of the types of this disease which inhibit sensation.

They are less common than Charcot-Marie-Tooth disease.

Symptoms of CMT usually begin in early childhood or early adulthood, but can begin later. Some people do not experience symptoms until their early thirties or forties. Usually, the initial symptom is foot drop early in the course of the disease. This can also cause hammer toe, where the toes are always curled. Wasting of muscle tissue of the lower parts of the legs may give rise to a "stork leg" or "inverted champagne bottle" appearance. Weakness in the hands and forearms occurs in many people as the disease progresses.

Loss of touch sensation in the feet, ankles and legs, as well as in the hands, wrists and arms occur with various types of the disease. Early and late onset forms occur with 'on and off' painful spasmodic muscular contractions that can be disabling when the disease activates. High-arched feet (pes cavus) or flat-arched feet (pes planus) are classically associated with the disorder. Sensory and proprioceptive nerves in the hands and feet are often damaged, while unmyelinated pain nerves are left intact. Overuse of an affected hand or limb can activate symptoms including numbness, spasm, and painful cramping.

Symptoms and progression of the disease can vary. Involuntary grinding of teeth as well as squinting are prevalent and often go unnoticed by the person affected. Breathing can be affected in some; so can hearing, vision, as well as the neck and shoulder muscles. Scoliosis is common, causing hunching and loss of height. Hip sockets can be malformed. Gastrointestinal problems can be part of CMT, as can difficulty chewing, swallowing, and speaking (due to atrophy of vocal cords). A tremor can develop as muscles waste. Pregnancy has been known to exacerbate CMT, as well as severe emotional stress. Patients with CMT must avoid periods of prolonged immobility such as when recovering from a secondary injury as prolonged periods of limited mobility can drastically accelerate symptoms of CMT.

Pain due to postural changes, skeletal deformations, muscle fatigue and cramping is fairly common in people with CMT. It can be mitigated or treated by physical therapies, surgeries, and corrective or assistive devices. Analgesic medications may also be needed if other therapies do not provide relief from pain. Neuropathic pain is often a symptom of CMT, though, like other symptoms of CMT, its presence and severity varies from case to case. For some people, pain can be significant to severe and interfere with daily life activities. However, pain is not experienced by all people with CMT. When neuropathic pain is present as a symptom of CMT, it is comparable to that seen in other peripheral neuropathies, as well as postherpetic neuralgia and complex regional pain syndrome, among other diseases.

At the beginning, affected individuals often notice the loss of pain and temperature sensation or all sensory modalities in their feet. As the disease progresses, the sensory abnormalities may extend up to the knees. However, they often do not notice sensory loss for a long time. Many affected individuals only become aware of the disease when they notice painless injuries and burns or when they seek medical advice for slowly healing wounds or foot ulcers. Foot ulcerations may appear due to permanent pressure, such as long walks or badly fitting shoes. Minor wounds or blisters may then lead to deep foot ulcerations. Once infection occurs, complications such as inflammation and destruction of the underlying bones may follow. Affected individuals who do not lose sensation may experience spontaneous pain. In addition, many affected individuals exhibit, to a variable degree, symmetrical distal muscle weakness and wasting.

HSAN I is characterized by marked sensory disturbances mainly as the loss of pain and temperature sensation in the distal parts of the lower limbs. The loss of sensation can also extend to the proximal parts of the lower limbs and the upper limbs as the disease progresses. Some affected individuals do not lose sensation, but instead experience severe shooting, burning, and lancinating pains in the limbs or in the trunk. Autonomic disturbances, if present, manifest as decreased sweating. The degree of motor disturbances is highly variable, even within families, ranging from absent to severe distal muscle weakness and wasting.

The disease progresses slowly, but often disables the affected individuals severely after a long duration. The onset of the disease varies between the 2nd and 5th decade of life, albeit congenital or childhood onset has occasionally been reported. With the progression of the disease, the affected individuals lose the ability to feel pain in their feet and legs. Minor injuries in the painless area can result in slow-healing wounds which, if not immediately recognized, can develop into chronic ulcerations. Once infection occurs, these ulcerations can result in severe complications that lead to foot deformity, such as inflammation of the underlying bones, spontaneous bone fractures, and progressive degeneration of weight-bearing joints. Furthermore, foot deformity promotes skin changes such as hyperkeratosis at pressure points. These complications may necessitate amputation of the affected foot.

Biopsies of severely affected sural nerve (short saphenous nerve) in patients with HSAN I showed evidence of neuronal degeneration. Only a very few myelinated fibers were observed some of which showed a sign of primary (segmental) demyelination. A reasonable number of unmyelinated axons remained, although the presence of stacks of flattened Schwann cell processes suggested unmyelinated axon loss. Electrophysiological testing provides additional evidence that neuronal degeneration underlies the disease. Sensory potentials are usually absent in the lower limbs but are often recordable or even normal in the upper limbs of the patients. In addition, motor conduction is slow, possibly implying a demyelinating process.

Neuropathy disorders usually have onset in childhood or young adulthood. Motor symptoms seem to be more predominant that sensory symptoms. Symptoms of these disorders include: fatigue, pain, lack of balance, lack of feeling, lack of reflexes, and lack of sight and hearing, which result from muscle atrophy. Patients can also suffer from high arched feet, hammer toes, foot drop, foot deformities, and scoliosis. These symptoms are a result of severe muscular weakness and atrophy. In patients suffering from demyelinating neuropathy, symptoms are due to slow nerve conduction velocities, however people with axonal degradation have average to normal nerve conduction velocities.

Onset usually occurs within the first two decades of life, commonly in the teenage years or the twenties. Life expectancy is normal. High arch of the foot (pes cavus) is common. Patients also have trouble controlling their hands, due to muscle loss on the thumb side of the index finger and palm below the thumb. It is rare for a person with this disorder to lose the ability to walk, though changes in gait may occur later in life.

Frequency of this disorder is unknown.

Hereditary sensory and autonomic neuropathy type I (HSAN I) or hereditary sensory neuropathy type I (HSN I) is a group of autosomal dominant inherited neurological diseases that affect the peripheral nervous system particularly on the sensory and autonomic functions. The hallmark of the disease is the marked loss of pain and temperature sensation in the distal parts of the lower limbs. The autonomic disturbances, if present, manifest as sweating abnormalities.

The beginning of the disease varies between adolescence and adulthood. Since affected individuals cannot feel pain, minor wounds or blisters in the painless area may not be immediately recognized and can develop into extensive and deep foot ulcerations. Once infection occurs, the complications such as inflammation and progressive destruction of the underlying bones may follow and may require amputation of the surrounding area.

HSAN I is the most common type among the five types of HSAN. As a heterogeneous group of diseases, HSAN I can be divided into five subtypes HSAN IA-E. Most of the genes associated with the diseases have been identified. However, the molecular pathways leading to the manifestation of the diseases are not fully understood. Therefore, the potential targets for therapeutic interventions are not known. Moreover, gene-based therapies for patients with the diseases are not available to date, hence supportive care is the only treatment available for the patients.

Onset occurs in infancy or early childhood, usually before 3 years of age. Progression is slow until the teenage years at which point it may accelerate, resulting in severe disability.

Symptoms are usually more severe and rapidly progressive than in the other more common Charcot–Marie–Tooth diseases. Some patients may never walk and solely use wheelchairs by the end of their first decade, while others may need only a cane (walking stick) or similar support through life.

Dejerine–Sottas disease is characterized by moderate to severe lower and upper extremity weakness and loss of sensation, which occur mainly in the lower legs, forearms, feet and hands. Loss of muscle mass and reduced muscle tone can occur as the disease progresses. Other symptoms may include pain in the extremities, curvature of the spine, clawed hands, foot deformities, ataxia, peripheral areflexia, and slow acquisition of motor skills in childhood. Symptoms that are less common can include limitation of eye movements, other eye problems such as nystagmus or anisocoria, or mild hearing loss.

In an individual with dHMN V, electromyography will show pure motor neuropathy, patterns of weakness without upper motor neuron damage, in the hands. Tendon reflexes will also appear normal. Clinical, electrophysiological, and pathological testing will show a lack of damage to sensory neurons, differentiating this disease from CMT.

Symptoms of the Roussy–Lévy syndrome mainly stem from nerve damage and the resulting progressive muscle atrophy. Neurological damage may result in absent tendon reflexes (areflexia), some distal sensory loss and decreased excitability of muscles to galvanic and faradic stimulation. Progressive muscle wasting results in weakness of distal limb muscles (especially the peronei), gait ataxia, pes cavus, postural tremors and static tremor of the upper limbs, kyphoscoliosis, and foot deformity.

These symptoms frequently translate into delayed onset of ability to walk, loss of coordination and balance, foot drop, and foot-bone deformities. They are usually first observed during infancy or early childhood, and slowly progress until about age 30, at which point progression may stop in some individuals, or symptoms may continue to slowly progress.

Hereditary Neuropathy with Liability to Pressure Palsy (HNPP) is a peripheral neuropathy, a disorder of the nerves. HNPP is a nerve disorder that affects the peripheral nerves,—pressure on the nerves can cause tingling sensations, numbness, pain, weakness, muscle atrophy, and even paralyzation of affected area. In normal individuals these symptoms disappear quickly but in sufferers of HNPP even a short period of pressure can cause the symptoms to occur. Palsies can last from minutes, days to weeks, or even months.

The symptoms may vary—some individuals report minor problems, whilst others experience severe discomfort and disability. In many cases the symptoms are mild enough to go unnoticed. The time period between episodes is known to vary between individuals. HNPP has not been found to alter the lifespan, although in some cases a decline in quality of life is noticed. Some sufferers (10-15%) report various pains growing in severity with progression of the disease. The nerves most commonly affected are the peroneal nerve at the fibular head (leg and feet), the ulnar nerve at the elbow (arm), and the median nerve at the wrist (palm, thumbs and fingers), but any peripheral nerve can be affected. HNPP is part of the group of hereditary motor and sensory neuropathy (HMSN) disorders and is linked to Charcot–Marie–Tooth disease (CMT).

Among the signs/symptoms of hereditary neuropathy with liability to pressure palsy are the following (different symptoms are caused by different nerves, such as the "foot drop" is caused by the "peroneal nerve"):

Sensory symptoms of small fiber neuropathy are highly variable. Common complaints include paresthesias, dysesthesias, and insensitivity to pain. "Paresthesias" are abnormal sensations. They are often described as numbness, burning, cold, prickling, pins and needles along with other symptoms. "Dysesthesias" are unpleasant sensations, either spontaneous or evoked. A light breeze, the feeling of clothes, or even a soft touch can cause pain.

Insensitivity to pain can be particular problem. One may be bleeding or have a skin injury without even knowing it.

Charcot–Marie–Tooth disease (CMT) is one of the hereditary motor and sensory neuropathies, a group of varied inherited disorders of the peripheral nervous system characterized by progressive loss of muscle tissue and touch sensation across various parts of the body. Currently incurable, this disease is the most commonly inherited neurological disorder, and affects approximately 1 in 2,500 people. CMT was previously classified as a subtype of muscular dystrophy.

The most distinctive clinical feature is the absence of overflow tears with emotional crying after age 7 months. This symptom can manifest less dramatically as persistent bilateral eye irritation. There is also a high prevalence of breech presentation. Other symptoms include weak or absent suck and poor tone, poor suck and misdirected swallowing, and red blotching of skin.

Symptoms in an older child with familial dysautonomia might include:

1. Delayed speech and walking

2. Unsteady gait

3. Spinal curvature

4. Corneal abrasion

5. Less perception in pain or temperature with nervous system.

6. Poor growth

7. Erratic or unstable blood pressure.

8. Red puffy hands

9. Dysautonomia crisis: a constellation of symptoms in response to physical and emotional stress; usually accompanied by vomiting, increased heart rate, increase in blood pressure, sweating, drooling, blotching of the skin and a negative change in personality.

Hereditary motor and sensory neuropathies (HMSN) is a name sometimes given to a group of different neuropathies which are all characterized by their impact upon both afferent and efferent neural communication. HMSN are characterised by atypical neural development and degradation of neural tissue. The two common forms of HMSN are either hypertrophic demyelinated nerves or complete atrophy of neural tissue. Hypertrophic condition causes neural stiffness and a demyelination of nerves in the peripheral nervous system, and atrophy causes the breakdown of axons and neural cell bodies. In these disorders, a patient experiences progressive muscle atrophy and sensory neuropathy of the extremities.

The term "hereditary motor and sensory neuropathy" was used mostly historically to denote the more common forms Charcot–Marie–Tooth disease (CMT). With the identification of a wide number of genetically and phenotypically distinct forms of CMT, the term HMSN is now used less frequently.

Like many polyneuropathies, the symptoms are length-dependent, starting in the longer nerves and progressively attack shorter nerves. This means that most often the symptoms start in the feet and progress upwards, and usually symptoms are more severe in the feet. Many patients have a widespread, length independent, or "patchy", presentation which is sporadic and can affect many nerves, including the trigeminal nerve or occipital nerve.

Patients with Fabry disease have isolated small fiber engagement, and can have a more widespread small fiber disruption.

Roussy–Lévy syndrome, also known as Roussy–Lévy hereditary areflexic dystasia, is a rare genetic disorder of humans that results in progressive muscle wasting. It is caused by mutations in the genes that code for proteins necessary for the functioning of the myelin sheath of the neurons, affecting the conductance of nerve signals and resulting in loss of muscles' ability to move.

The condition affects people from infants through adults and is inherited in an autosomal dominant manner. Currently, no cure is known for the disorder.

Dejerine–Sottas disease, also known as Dejerine–Sottas syndrome, Dejerine–Sottas neuropathy, progressive hypertrophic interstitial polyneuropathy of childhood and onion bulb neuropathy (and, "hereditary motor and sensory polyneuropathy type III" and "Charcot–Marie–Tooth disease type 3"), is a hereditary neurological disorder characterised by damage to the peripheral nerves and resulting progressive muscle wasting. The condition is caused by mutations in a various genes and currently has no known cure.

The disorder is named for Joseph Jules Dejerine and Jules Sottas, French neurologists who first described it.

Neuritis is a general term for inflammation of a nerve or the general inflammation of the peripheral nervous system. Symptoms depend on the nerves involved, but may include pain, paresthesia (pins-and-needles), paresis (weakness), hypoesthesia (numbness), anesthesia, paralysis, wasting, and disappearance of the reflexes.

Causes of neuritis include:

Those with diseases or dysfunctions of their nerves may present with problems in any of the normal nerve functions. Symptoms vary depending on the types of nerve fiber involved.In terms of sensory function, symptoms commonly include loss of function ("negative") symptoms, including , tremor, impairment of balance, and gait abnormality. Gain of function (positive) symptoms include tingling, pain, itching, crawling, and pins-and-needles.

Motor symptoms include loss of function ("negative") symptoms of weakness, tiredness, muscle atrophy, and gait abnormalities; and gain of function ("positive") symptoms of cramps, and muscle twitch (fasciculations).

In the most common form, length-dependent peripheral neuropathy, pain and parasthesia appears symmetrically and generally at the terminals of the longest nerves, which are in the lower legs and feet. Sensory symptoms generally develop before motor symptoms such as weakness. Length-dependent peripheral neuropathy symptoms make a slow ascent of leg, while symptoms may never appear in the upper limbs; if they do, it will be around the time that leg symptoms reach the knee. When the nerves of the autonomic nervous system are affected, symptoms may include constipation, dry mouth, difficulty urinating, and dizziness when standing.

People with this disorder are very likely to injure themselves in ways that would normally be prevented by feeling pain. For example, a patient could burn themselves severely and not even notice. The main features of the disorder are lack of pain sensation, painless injuries of the arms, legs, and oral structures, hyperthermia during hot weather because of inability to sweat, syndromic intellectual disability as a result of hyperthermia, infection and scarring of the tongue, lips and gums, chronic infections of bones and joints, bone fractures, multiple scars, osteomyelitis and joint deformities, which may lead to amputation. Other common problems are eye related, such as infection due to the sufferers rubbing them too hard, too frequently or scratching them during sleep. In addition, patients typically lack unmyelinated and small myelinated nerve fibers in the dorsal root ganglion. Both are responsible for transmitting pain signals. In addition, patients' sweat glands are normal in both structure and function, though they lack innervations by small diameter neurons.

Familial dysautonomia (FD), sometimes called Riley–Day syndrome and hereditary sensory and autonomic neuropathy type III (HSAN-III), is a disorder of the autonomic nervous system which affects the development and survival of sensory, sympathetic and some parasympathetic neurons in the autonomic and sensory nervous system resulting in variable symptoms, including insensitivity to pain, inability to produce tears, poor growth, and labile blood pressure (episodic hypertension and postural hypotension). People with FD have frequent vomiting crises, pneumonia, problems with speech and movement, difficulty swallowing, inappropriate perception of heat, pain, and taste, as well as unstable blood pressure and gastrointestinal dysmotility. FD does not affect intelligence. Originally reported by Drs. Conrad Milton Riley (1913–2005) and Richard Lawrence Day (1905–1989) in 1949, FD is one example of a group of disorders known as hereditary sensory and autonomic neuropathies (HSAN). All HSAN are characterized by widespread sensory dysfunction and variable autonomic dysfunction caused by incomplete development of sensory and autonomic neurons. The disorders are believed to be genetically distinct from each other.

Congenital insensitivity to pain with anhidrosis may be misdiagnosed for leprosy, based on similar symptoms of severe injuries to the hands and feet.

Hereditary motor and sensory neuropathy with proximal dominance (HMSN-P) is an autosomal dominant neurodegenerative disorder that is defined by extensive involuntary and spontaneous muscle contractions, asthenia, and atrophy with distal sensory involvement following. The disease starts presenting typically in the 40s and is succeeded by a slow and continuous onslaught. Muscle spasms and muscle contractions large in number are noted, especially in the earliest stages. The presentation of HMSN-P is quite similar to amyotrophic lateral sclerosis and has common neuropathological findings. Sensory loss happens as the disease progresses, but the amount of sensation lost varies from case to case. There have been other symptoms of HMSN-P reported such as urinary disturbances and a dry cough.

Two large families in Japan have been identified with the disease locus to chromosome 3q. From descendants of Japan, HMSN-P was brought to Brazil, from there it is a pretty isolated disease. Through clinical studies, researchers identified that TFG mutations on chromosome 3q13.2 causes HMSN-P. "The presence of TFG/ubiquitin- and/or TDP-43-immunopositive cytoplasmic inclusions in motor neurons and cytosolic aggregation composed of TDP-43 in cultured cells expressing mutant TFG indicate a novel pathway of motor neuron death"