Maturity-onset diabetes of the young

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Maturity-onset diabetes of the young (MODY) is a group of several conditions characterized by abnormally high levels of blood glucose, also called blood sugar. These forms of diabetes typically begin before age 30, although they can occur later in life. In MODY, elevated blood glucose arises from reduced production of insulin, which is a hormone produced in the pancreas that helps regulate blood glucose levels. Specifically, insulin controls how much glucose (a type of sugar) is passed from the blood into cells, where it is used as an energy source.

The different types of MODY are distinguished by their genetic causes. The most common types are HNF1A-MODY (also known as MODY3), accounting for 50 to 70 percent of cases, and GCK-MODY (MODY2), accounting for 30 to 50 percent of cases. Less frequent types include HNF4A-MODY (MODY1) and renal cysts and diabetes (RCAD) syndrome (also known as HNF1B-MODY or MODY5), which each account for 5 to 10 percent of cases. At least ten other types have been identified, and these are very rare.

HNF1A-MODY and HNF4A-MODY have similar signs and symptoms that develop slowly over time. Early signs and symptoms in these types are caused by high blood glucose and may include frequent urination (polyuria), excessive thirst (polydipsia), fatigue, blurred vision, weight loss, and recurrent skin infections. Over time uncontrolled high blood glucose can damage small blood vessels in the eyes and kidneys. Damage to the light-sensitive tissue at the back of the eye (the retina) causes a condition known as diabetic retinopathy that can lead to vision loss and eventual blindness. Kidney damage (diabetic nephropathy) can lead to kidney failure and end-stage renal disease (ESRD). While these two types of MODY are very similar, certain features are particular to each type. For example, babies with HNF4A-MODY tend to weigh more than average or have abnormally low blood glucose at birth, even though other signs of the condition do not occur until childhood or young adulthood. People with HNF1A-MODY have a higher-than-average risk of developing noncancerous (benign) liver tumors known as hepatocellular adenomas.

GCK-MODY is a very mild type of the condition. People with this type have slightly elevated blood glucose levels, particularly in the morning before eating (fasting blood glucose). However, affected individuals often have no symptoms related to the disorder, and diabetes-related complications are extremely rare.

RCAD is associated with a combination of diabetes and kidney or urinary tract abnormalities (unrelated to the elevated blood glucose), most commonly fluid-filled sacs (cysts) in the kidneys. However, the signs and symptoms are variable, even within families, and not everyone with RCAD has both features. Affected individuals may have other features unrelated to diabetes, such as abnormalities of the pancreas or liver or a form of arthritis called gout.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

MODY can be caused by a mutation in one of several genes. HNF1A-MODY, GCK-MODY, HNF4A-MODY, and RCAD, are caused by mutations in the HNF1A, GCK, HNF4A, and HNF1B gene, respectively. All of these genes provide instructions for making proteins involved in the production of insulin to control blood glucose levels in the body. In particular, the proteins are important in specialized cells in the pancreas called beta cells, which secrete insulin.

The proteins produced from the HNF1A, HNF4A, and HNF1B genes all act as transcription factors, which means they control the activity of other genes. In particular, these proteins regulate genes that direct the development and function of beta cells. HNF1A, HNF4A, or HNF1B gene mutations result in production of an altered transcription factor that is unable to function normally. These changes alter gene activity in cells, impairing normal beta cell development and function. As a result, beta cells are less able than normal to produce insulin in response to glucose in the blood, which means the body cannot control blood glucose. Elevated blood glucose results in the signs and symptoms of MODY. Some of these MODY-related genes play roles in the development of other body systems, in addition to beta cells. Disrupted development of these systems underlies additional signs and symptoms in particular forms of MODY. For example, the HNF1B gene is involved in kidney development, which helps explain the kidney abnormalities in people with RCAD.

The protein produced from the GCK gene acts as a sensor that recognizes when the amount of glucose in the blood rises. In response, the protein helps stimulate the release of insulin from beta cells so glucose can be taken up and used by cells for energy. This protein also helps determine when excess glucose should be taken into liver cells and stored. Mutations in the GCK gene limit the protein's ability to sense a rise in blood glucose, so levels remain elevated.

Other genes involved in controlling blood glucose cause rare types of MODY. It is likely that additional genes that have not been identified are also involved in the condition.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

MODY 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

MODY is estimated to account for 1 to 3 percent of all cases of diabetes.

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.

Abnormal C-peptide level · Frequent (79-30%)

Any deviation from the normal concentration of C-peptide in the blood circulation.

Abnormal circulating insulin concentration · Frequent (79-30%)

An abnormal concentration of insulin in the body.

Abnormal oral glucose tolerance · Frequent (79-30%)

An abnormal resistance to glucose, i.e., a reduction in the ability to maintain glucose levels in the blood stream within normal limits following oral administration of glucose.

Elevated hemoglobin A1c · Frequent (79-30%)

An increased concentration of hemoglobin A1c (HbA1c), which is the product of nonenzymatic attachment of a hexose molecule to the N-terminal amino acid of the hemoglobin molecule. This reaction is dependent on blood glucose concentration, and therefore reflects the mean glucose concentration over the previous 8 to 12 weeks. The HbA1c level provides a better indication of long-term glycemic control than one-time blood or urinary glucose measurements.

Glucose intolerance · Frequent (79-30%)

Glucose intolerance (GI) can be defined as dysglycemia that comprises both prediabetes and diabetes. It includes the conditions of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) and diabetes mellitus (DM).

Glycosuria · Frequent (79-30%)

An increased concentration of glucose in the urine.

Hyperglycemia · Frequent (79-30%)

An increased concentration of glucose in the blood.

Hypoinsulinemia · Frequent (79-30%)

A decreased concentration of insulin in the blood.

Other findings in the same source

From: Orphanet

Additional reported features include Hyperinsulinemic hypoglycemia (Occasional (29-5%)); Insulin-resistant diabetes mellitus (Occasional (29-5%)); Intrauterine growth retardation (Occasional (29-5%)); Large for gestational age (Occasional (29-5%)); Nephropathy (Occasional (29-5%)); Overweight (Occasional (29-5%)); Retinopathy (Occasional (29-5%)); Neonatal hypoglycemia (Occasional (29-5%)); Transient neonatal diabetes mellitus (Occasional (29-5%)); Abnormality of the genitourinary system (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Maturity-onset diabetes of the young is Endocrinology, with a endocrinologist 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 hormone or metabolic finding is important in this case?
• How should test timing and current medicines be taken into account?
• What follow-up would show whether the care plan is working?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Maturity-onset diabetes of the young. 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.