Hereditary sensory and autonomic neuropathy type IE

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Hereditary sensory and autonomic neuropathy type IE (HSAN IE) is a disorder that affects the nervous system. It is characterized by three main features: hearing loss, a decline of intellectual function (dementia), and a worsening loss of sensation in the feet and legs (peripheral neuropathy).

People with HSAN IE develop hearing loss that is caused by abnormalities in the inner ear (sensorineural hearing loss). The hearing loss, which affects both ears, gets worse over time and usually progresses to moderate or severe deafness between the ages of 20 and 35.

Affected individuals experience dementia typically beginning in their thirties. In some people with HSAN IE, changes in personality, such as irritability, apathy, or lack of impulse control, become apparent before problems with thinking skills.

Peripheral neuropathy is caused by impaired function of nerve cells called sensory neurons, which transmit information about sensations such as pain, temperature, and touch. Loss of sensation in the feet and legs, which usually begins in adolescence or early adulthood in people with HSAN IE and worsens over time, can cause difficulty walking. Affected individuals may not be aware of injuries to their feet, which can lead to complications such as open sores and infections. If these complications are severe, amputation of the affected areas may be required.

Some people with HSAN IE also experience recurrent seizures (epilepsy) and sleep problems. The severity of the signs and symptoms of HSAN IE and their age of onset are variable, even among affected members of the same family.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

HSAN IE is caused by mutations in the DNMT1 gene, which provides instructions for making an enzyme called DNA methyltransferase 1. This enzyme is involved in DNA methylation, which is the addition of methyl groups, consisting of one carbon atom and three hydrogen atoms, to DNA molecules.

DNA methylation is important in many cellular functions. These include determining whether the instructions in a particular segment of DNA are carried out or suppressed (gene silencing), regulating reactions involving proteins and fats (lipids), and controlling the processing of chemicals that relay signals in the nervous system (neurotransmitters). DNA methyltransferase 1 is active in the adult nervous system. Although its specific function is not well understood, the enzyme may help regulate neuron maturation and specialization (differentiation), the ability of neurons to migrate where needed and connect with each other, and neuron survival.

DNMT1 gene mutations that cause HSAN IE affect the enzyme's methylation function, resulting in abnormalities in the maintenance of the neurons that make up the nervous system. However, it is not known how the mutations cause the specific signs and symptoms of HSAN IE.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In most cases, an affected person inherits the mutation from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

HSAN IE is a rare disorder; its prevalence is unknown. Small numbers of affected families have been identified in populations around the world.

Which doctor should you see?

The suggested department for discussing Hereditary sensory and autonomic neuropathy type IE is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Hereditary sensory and autonomic neuropathy type IE. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.