Affected individuals typically get open sores (ulcers) on their feet or hands or infections of the soft tissue of the fingertips (whitlows) that are slow to heal.

The signs and symptoms of hereditary sensory neuropathy type 1 typically appear during a person's teens or twenties.

While the features of this disorder tend to worsen over time, affected individuals have a normal life expectancy if signs and symptoms are properly treated.

Since the affected individuals cannot feel pain, minor injuries in this area may not be immediately recognized and may develop into extensive ulcerations.

Examinations of the nerve structure and function showed signs of neuronal degeneration such as a marked reduction in the number of myelinated fibers and axonal loss.

A lack of functional SPT enzyme leads to a decrease in sphingolipid production and a harmful buildup of certain byproducts.

A decrease in sphingolipids disrupts the formation of myelin, causing nerve cells to become less efficient and eventually die.

This gradual destruction of nerve cells results in loss of sensation and muscle weakness in people with hereditary sensory neuropathy type 1.

In some affected people, the condition may also cause mild abnormalities of the autonomic nervous system, which controls involuntary body functions such as heart rate, digestion, and breathing.

Affected individuals often have injuries and fractures in their hands, feet, limbs, and joints that go untreated because of the inability to feel pain.

Type 2, congenital sensory neuropathy (also historically known as Morvan's disease[4]), is characterized by onset of symptoms in early infancy or childhood.

The loss of neurons leads to the inability to feel pain, temperature, and touch sensations and to the impairment of the autonomic nervous system seen in people with HSAN2.

The disorder disturbs cells in the autonomic nervous system, which controls involuntary actions such as digestion, breathing, production of tears, and the regulation of blood pressure and body temperature.

It also affects the sensory nervous system, which controls activities related to the senses, such as taste and the perception of pain, heat, and cold.

Older infants and young children with familial dysautonomia may hold their breath for prolonged periods of time, which may cause a bluish appearance of the skin or lips (cyanosis) or fainting.

Additional signs and symptoms in school-age children include bed wetting, episodes of vomiting, reduced sensitivity to temperature changes and pain, poor balance, abnormal curvature of the spine (scoliosis), poor bone quality and increased risk of bone fractures, and kidney and heart problems.

They may experience a sharp drop in blood pressure upon standing (orthostatic hypotension), which can cause dizziness, blurred vision, or fainting.

About one-third of children with familial dysautonomia have learning disabilities, such as a short attention span, that require special education classes.

Type 3, familial dysautonomia (FD) or Riley-Day syndrome, is an autosomal recessive disorder seen predominantly in Jews of eastern European descent.

This mutation can disrupt how information in the IKBKAP gene is pieced together to make a blueprint for the production of IKAP protein.

Critical activities in brain cells are probably disrupted by reduced amounts or the absence of IKAP protein, leading to the signs and symptoms of familial dysautonomia.

The ability to sense all pain (including visceral pain) is absent, resulting in repeated injuries including: oral self-mutilation (biting of tongue, lips, and buccal mucosa); biting of fingertips; bruising, scarring, and infection of the skin; multiple bone fractures (many of which fail to heal properly); and recurrent joint dislocations resulting in joint deformity.

The sensory loss is due to abnormal functioning of small, unmyelinated nerve fibers and portions of the spinal cord that control responses to pain and temperature as well as other involuntary or automatic body processes.

The histopathology of peripheral nerve biopsy reveals absent small unmyelinated fibers and mitochondria are abnormally enlarged.

Interventions for behavioral, developmental and motor delays, as well as educational and social support for school-age children and adolescents, are recommended.

During and following surgical procedures, potential complications to identify and manage promptly include hyper- or hypothermia and inadequate sedation, which may trigger unexpected movement and result in secondary injuries.

Binding of the NGFβ protein to its receptor transmits signals to the cell to grow and to mature and take on specialized functions (differentiate).

Mutation of the NGF gene leads to the production of a protein that cannot bind to the receptor and does not transmit signals properly.

Hereditary sensory and autonomic neuropathy type 6 (HSAN6), also known as familial dysautonomia with contractures,[5] is a severe autosomal recessive disorder characterized by neonatal hypotonia, respiratory and feeding difficulties, lack of psychomotor development, and autonomic abnormalities including labile cardiovascular function, lack of corneal reflexes leading to corneal scarring, areflexia, and absent axonal flare response after intradermal histamine injection.

With the intracellular transport system disrupted by a mutation in DST, the autophagosomes are unable to carry away the debris, which builds up at the ends of the neuron, leading to damage.