Hyperinsulinism due to HNF1A deficiency

What it is

From: Orphanet

Hyperinsulinism due to HNF1A deficiency is a form of diazoxide-sensitive diffuse hyperinsulinism (DHI), characterized by transient or persistent hyperinsulinemic hypoglycemia (HH) in infancy that is responsive to diazoxide, evolving in to maturity-onset diabetes of the young subtype 1 (MODY-1) later in life.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Excessive insulin response to glucagon test · Very frequent (99-80%)

An abnormally high increase in insulin levels following a glucagon stimulation test.

Hyperinsulinemic hypoglycemia · Very frequent (99-80%)

An increased concentration of insulin combined with a decreased concentration of glucose in the blood.

Increased C-peptide level · Very frequent (99-80%)

The concentration of C-peptide in the blood circulation is above the upper limit of normal.

Neonatal hypotonia · Very frequent (99-80%)

Muscular hypotonia (abnormally low muscle tone) manifesting in the neonatal period.

Decreased circulating free fatty acid level · Very frequent (99-80%)

Neonatal hypoglycemia · Very frequent (99-80%)

Agitation · Frequent (79-30%)

A state of excessive motor activity that is associated with mental distress or a feeling of substantial unease or inner tension. Distinguished from restlessness by the increased level of emotional distress and negative intensity of the experience. Agitation has a significant level of physical activity that is typically threatening to the self or others.

Drowsiness · Frequent (79-30%)

Abnormal feeling of sleepiness or difficulty staying awake.

Episodic hyperhidrosis · Frequent (79-30%)

Intermittent episodes of abnormally increased perspiration.

Hyperinsulinemia · Frequent (79-30%)

An increased concentration of insulin in the blood.

Hypoketotic hypoglycemia · Frequent (79-30%)

A decreased concentration of glucose in the blood associated with a reduced concentration of ketone bodies.

Large for gestational age · Frequent (79-30%)

The term large for gestational age applies to babies whose birth weight lies above the 90th percentile for that gestational age.

Maturity-onset diabetes of the young · Frequent (79-30%)

The term Maturity-onset diabetes of the young (MODY) was initially used for patients diagnosed with fasting hyperglycemia that could be treated without insulin for more than two years, where the initial diagnosis was made at a young age (under 25 years). Thus, MODY combines characteristics of type 1 diabetes (young age at diagnosis) and type 2 diabetes (less insulin dependence than type 1 diabetes). The term MODY is now most often used to refer to a group of monogenic diseases with these characteristics. Here, the term is used to describe hyperglycemia diagnosed at a young age with no or minor insulin dependency, no evidence of insulin resistance, and lack of evidence of autoimmune destruction of the beta cells.

Neurodevelopmental abnormality · Frequent (79-30%)

A deviation from normal of the neurological development of a child, which may include any or all of the aspects of the development of personal, social, gross or fine motor, and cognitive abilities.

Other findings in the same source

From: Orphanet

Additional reported features include Pallor (Frequent (79-30%)); Palpitations (Frequent (79-30%)); Reactive hypoglycemia (Frequent (79-30%)); Tachycardia (Frequent (79-30%)); Fasting hypoglycemia (Frequent (79-30%)); Hypoglycemic seizures (Frequent (79-30%)); Feeding difficulties (Occasional (29-5%)); Hypoglycemic coma (Occasional (29-5%)); Ketotic hypoglycemia (Occasional (29-5%)); Lethargy (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Infancy; Neonatal

Inheritance in the source

From: Orphanet

Autosomal dominant

Frequency and the population described

From: Orphanet

Reported case(s): 2.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal dominant pattern means that one altered copy of a relevant gene can be sufficient for the condition. Some affected people inherit the change; others have a new change without an affected parent. The precise finding, family history and condition determine what this means for relatives.

Which doctor should you see?

The suggested department for discussing Hyperinsulinism due to HNF1A deficiency is Metabolic Medicine, with a metabolic specialist / clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with metabolic specialist / clinical geneticist referral.

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.

• Is a biochemical or molecular result needed to clarify the diagnosis?
• Does this condition require an individual plan for illness or reduced food intake?
• Should nutrition advice come from a specialist metabolic dietitian?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Hyperinsulinism due to HNF1A deficiency. 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.