Maturity-onset diabetes of the young type 1 is a genetic form of diabetes that usually starts in childhood, the teens, or early adulthood. People with Maturity-onset diabetes of the young type 1 often have high blood sugar with thirst, frequent urination, tiredness, and sometimes weight loss. It tends to be lifelong, and the pattern can vary in severity between families and across ages. Treatment often includes insulin, careful meal planning, physical activity, and regular glucose monitoring, and many people manage it well. The risk of death is generally low with modern care, but untreated or long-term high sugars can lead to serious complications.
Overview
Maturity-onset diabetes of the young type 1Symptoms
Maturity-onset diabetes of the young type 1 often causes increased thirst, frequent urination, tiredness, and unintended weight loss from high blood sugar. Some have blurry vision or yeast or urinary infections. Many notice mild symptoms or none until routine tests.
Outlook and prognosis
Most people with maturity‑onset diabetes of the young type 1 (MODY 1) do well with early diagnosis and tailored treatment. Blood sugar often stabilizes with the right plan, lowering risks to eyes, kidneys, heart, and nerves. Regular follow‑up and family screening help long‑term health.
Causes and risk factors
Maturity-onset diabetes of the young type 1 results from HNF4A gene changes, usually inherited in an autosomal-dominant pattern. Risk is higher with an affected parent or family history; new mutations occur. Lifestyle and environmental factors influence severity, not cause it.
Genetic influences
Genetics is central in Maturity-onset diabetes of the young type 1 (MODY1). Single inherited variants in the HNF4A gene typically cause it, following an autosomal dominant pattern. One altered copy often leads to MODY1, with strong family clustering.
Diagnosis
Diagnosis of Maturity-onset diabetes of the young type 1 relies on early-onset diabetes, a strong family history, and clinical patterns; genetic testing of HNF4A confirms it.
Treatment and drugs
Maturity-onset diabetes of the young type 1 is usually managed with low-dose sulfonylurea tablets, which help the pancreas release insulin more effectively. Many living with MODY 1 can delay or reduce insulin needs with this approach. Care also includes regular glucose checks, healthy eating, physical activity, and routine follow-up with diabetes specialists.
Symptoms
Maturity-onset diabetes of the young type 1 (MODY1) often shows up in the teens or 20s, and many people feel well at first. Early features of Maturity-onset diabetes of the young type 1 can be subtle and may first be found on routine bloodwork. Features vary from person to person and can change over time. When present, signs mirror other forms of high blood sugar—more thirst, more frequent urination, tiredness, and sometimes blurry vision.
Many people feel well and have no clear warning signs at first. High blood sugar is often first spotted on a routine blood test or during a health check. Sometimes it’s noticed in pregnancy screening.
High glucose is commonly found in the teenage years or early adulthood. It can also appear in childhood or later life in some families. The pattern can stay mild for years.
Feeling unusually thirsty and peeing more often can occur as glucose rises. These signs may be mild at first in MODY1. Nighttime bathroom trips may be the first clue.
Low energy and blurry vision can happen when glucose runs high. These changes often improve as levels come down. Headaches can sometimes accompany these spells.
How people usually first notice Maturity-onset diabetes of the young type 1?
People often first notice maturity-onset diabetes of the young type 1 (MODY1) when routine blood work shows high blood sugar despite being otherwise well, sometimes after a mild illness or during a school or work physical. Because MODY1 is inherited in an autosomal dominant pattern, a family history of early-onset diabetes across generations can be a key clue, and teens or young adults may have thirst, frequent urination, or unexpected weight loss without the typical features of type 1 diabetes. Doctors often recognize the first signs of MODY1 when antibody tests for type 1 diabetes are negative, C‑peptide shows the body still makes insulin, and elevated glucose appears at a young age, prompting genetic testing to confirm how MODY1 is first noticed.
Types of Maturity-onset diabetes of the young type 1
Maturity-onset diabetes of the young type 1 (MODY 1) is a genetic form of diabetes caused by changes in a single gene, and there are a few recognized variants within this one condition. These variants are defined by the exact change in the HNF4A gene, which can influence how early symptoms appear, blood sugar patterns, and sensitivity to certain diabetes medications. People may notice different sets of symptoms depending on their situation. When people search for types of MODY 1, they’re usually asking about these gene-based variants and how they shape day-to-day management.
HNF4A-truncating variants
These often lead to earlier-onset diabetes in the teens or 20s with fasting or after-meal high sugars. People can be quite sensitive to sulfonylureas, so lower doses may control glucose well. Newborns in the family may have higher birth weight and brief low blood sugar after birth.
HNF4A-missense variants
These changes can cause diabetes that appears from adolescence to mid-adulthood with milder early symptoms. After-meal glucose spikes may stand out more than fasting levels. Many respond to sulfonylureas, though the dose needed can vary by variant.
Promoter or regulatory variants
Changes that affect gene regulation can shift how strongly the HNF4A gene is “turned on.” Onset can vary from youth to adulthood, and severity ranges from mild to more pronounced hyperglycemia. Family patterns can help clarify the expected course.
Neonatal-influencing variants
Some HNF4A changes are linked with higher birth weight and transient low sugars in newborns. Later in life, these individuals may develop MODY 1 with typical features such as progressive high blood sugar. Not everyone with this neonatal pattern will have the same timing or severity.
What genetics can tell you about symptoms
People with MODY1 (HNF4A gene changes) often develop mild high blood sugar in childhood, then worsening in the teens or 20s, and babies may be unusually large at birth or have low blood sugar soon after. These symptoms reflect how HNF4A variants reduce insulin production.
Causes and risk factors
Maturity-onset diabetes of the young type 1 is driven by a change in the HNF4A gene, usually inherited from a parent.
The gene change can also be new in a family, and a parent who carries it has a 50% chance of passing it on.
A strong family history of diabetes diagnosed in the teens or early adulthood is the main risk factor for maturity-onset diabetes of the young type 1.
Weight, diet, illness, puberty, or pregnancy do not cause MODY 1, but they can influence when high blood sugar starts and how severe it becomes.
Genes set the stage, but environment and lifestyle often decide how the story unfolds.
Environmental and biological risk factors
Planning a pregnancy can bring practical questions about what may raise the odds of a child being born with Maturity-onset diabetes of the young type 1 (MODY1). Doctors often group risks into internal (biological) and external (environmental). For this condition, influences mostly center on events before conception; environment plays a limited role, and overall chances remain low. The points below highlight environmental risk factors for Maturity-onset diabetes of the young type 1 and related biological factors where evidence exists.
As men age, small copying errors can occur more often when sperm are formed. Very rarely, this can result in a child being born with MODY1. The overall chance remains low.
Strong radiation to the pelvis before conception can damage egg or sperm. This may slightly raise the chance of new changes passed to a child. Routine medical X-rays use much lower doses and are not linked to a measurable increase.
Some chemotherapy drugs and pelvic radiation can injure reproductive cells. Conception soon after treatment may carry a small, temporary rise in the chance of changes that appear in a future pregnancy. Doctors may advise waiting a period before trying to conceive.
Genetic risk factors
Maturity-onset diabetes of the young type 1 (MODY1) stems from a single gene—HNF4A—that plays a key role in insulin production. These inherited changes often run in families and can lead to diabetes at a younger age without autoimmune markers. Some risk factors are inherited through our genes. Understanding how this gene is passed down helps explain why several relatives across generations may be affected.
HNF4A gene change: A disease-causing change in the HNF4A gene is the core driver of MODY1. It disrupts how insulin-producing cells work, increasing the chance of early-onset diabetes. Different changes in this gene can shift the age when diabetes first appears.
Autosomal dominant pattern: MODY1 follows an autosomal dominant pattern, meaning one changed copy of HNF4A is enough to raise risk. Each child of an affected parent has a 50% chance of inheriting the variant. This applies to all sexes equally.
Family history clues: Diabetes appearing in multiple generations, often in teens or early adulthood, points toward MODY1. Relatives with non-autoimmune diabetes at a young age may share the same HNF4A change. A consistent pattern across parent and child is common.
De novo variant: A new (de novo) HNF4A change can cause MODY1 even when no relatives are affected. This is uncommon, but it means family history may be absent in some cases. If parents test negative for the variant, siblings usually have a low chance of having it.
Variable expression: Not everyone with the same HNF4A change develops diabetes at the same age or with the same severity. This variability can make MODY1 harder to recognize in a family.
Known family variant: If a specific HNF4A change is identified in a family, relatives who carry the same change have a high chance of MODY1. Recognizing early symptoms of Maturity-onset diabetes of the young type 1 can prompt timely checks and treatment. Genetic counseling can help map out who in the family may benefit from testing.
Lifestyle risk factors
Lifestyle habits do not cause Maturity-onset diabetes of the young type 1 (MODY1), but they strongly influence day-to-day glucose levels and long-term complications. Understanding how lifestyle affects Maturity-onset diabetes of the young type 1 can help you smooth glucose swings and reduce medication needs. The elements below describe practical ways lifestyle factors shape glycemic control in MODY1.
High-fiber, minimally processed carbs slow glucose absorption and blunt post-meal spikes in MODY1. Lower-glycemic choices reduce demand on the HNF4A-impaired beta cells.
Sweet drinks cause rapid glucose surges that MODY1 beta cells cannot match with insulin. Replacing them with water or unsweetened options helps prevent sharp spikes.
Regular, balanced meals prevent large glucose swings when insulin secretion is limited in MODY1. Long fasting followed by heavy carbs can trigger exaggerated post-meal rises.
Aerobic and resistance exercise increase muscle glucose uptake independent of insulin, easing the burden on impaired beta cells in MODY1. Consistent activity can lower post-meal peaks and reduce medication needs.
Risk prevention
You can’t fully prevent Maturity-onset diabetes of the young type 1 (MODY type 1) because it’s caused by a genetic change passed through families, but you can lower the chance of high blood sugar and long-term complications. Prevention is about lowering risk, not eliminating it completely. Healthy daily habits, the right medication plan, and regular check-ins make a real difference over time. Knowing early symptoms of MODY type 1—like extra thirst, frequent urination, or unexpected weight loss—can also prompt earlier testing and treatment in families at risk.
If MODY type 1 runs in your family, ask about genetic testing and screening for relatives. Knowing your risks can guide which preventive steps matter most.
Choose regular meals with fiber-rich vegetables, whole grains, lean proteins, and healthy fats to smooth out blood sugar. Limiting sugary drinks and large refined-carb portions can reduce blood sugar spikes.
Aim for daily activity, like brisk walking or cycling, to help your body use insulin more effectively. Even short bouts across the day can improve blood sugar control.
Keeping a steady, healthy weight can delay rising sugars and lower strain on the pancreas in MODY type 1. Small, steady changes are more sustainable than big swings.
Transmission
Maturity-onset diabetes of the young type 1 is not infectious—you can’t catch it or pass it to someone through contact, coughs, or shared items. It doesn’t spread like viruses or bacteria.
Instead, it runs in families due to a single gene change. This is known medically as autosomal dominant inheritance: if a parent carries the gene change, each child has a 50% chance of inheriting it. Sometimes the change happens for the first time in someone with no family history (a new mutation), so genetic transmission of Maturity-onset diabetes of the young type 1 can begin in one generation and then be passed to future children.
When to test your genes
Consider genetic testing if diabetes appeared before age 25, runs through several generations, or if you’re not overweight yet need low insulin doses and have stable sugars. Test when treatment choices hinge on the result (e.g., switching from insulin to sulfonylureas). Discuss timing with your clinician and a genetic counselor.
Diagnosis
When doctors evaluate possible Maturity-onset diabetes of the young type 1 (MODY1), they combine your story, family pattern, and a few targeted blood tests, then confirm with a genetic test. Family history is often a key part of the diagnostic conversation. The goal is to tell it apart from type 1 or type 2 diabetes so treatment and screening fit you and your relatives. A genetic diagnosis of Maturity-onset diabetes of the young type 1 can also guide who else in the family may benefit from testing.
Doctors look for diabetes starting in youth or early adulthood, often in people who are not overweight. Steady blood sugar patterns without episodes of ketoacidosis can raise suspicion for MODY1.
A pattern of diabetes across several generations suggests an inherited form. Seeing parent-to-child transmission supports the possibility of MODY1.
Fasting glucose, HbA1c, or an oral glucose tolerance test show how the body handles sugar over time. These help document diabetes and its severity.
Tests check for diabetes-related antibodies often present in type 1 diabetes. A negative result supports looking for MODY1 or other non-autoimmune causes.
Stages of Maturity-onset diabetes of the young type 1
Maturity-onset diabetes of the young type 1 does not have defined progression stages. It’s a genetic form of diabetes that usually shows up in the teen years or early adulthood and is identified by consistent patterns in blood sugar and a specific gene change, rather than a predictable step-by-step decline. Different tests may be suggested to help confirm the diagnosis and guide treatment. These often include blood sugar and HbA1c checks, tests to rule out type 1 autoimmunity, C‑peptide to see how much insulin your body is making, and genetic testing; early symptoms of Maturity-onset diabetes of the young type 1 like increased thirst and frequent urination may be the reason testing starts.
Outlook and prognosis
Daily routines often adapt as people with Maturity-onset diabetes of the young type 1 (MODY 1) learn how their blood sugar responds to meals, activity, stress, and illness. Many living with MODY 1 can keep glucose in range for years with tailored treatment and steady habits. In medical terms, the long-term outlook is often shaped by both genetics and lifestyle. Early symptoms of MODY 1 can be mild—or even missed—so getting diagnosed and starting a plan early often prevents bigger swings later.
Looking at the long-term picture can be helpful. Over time, most people with MODY 1 need medicines that support insulin production or action, and some eventually transition to insulin if the pancreas makes less over the years. Complications linked to long-standing high glucose—eye, kidney, nerve, and heart problems—are possible, especially if sugars stay high; keeping A1C in target lowers those risks significantly. The risk of early death from MODY 1 itself appears low when blood sugars are well managed, but cardiovascular risk follows the same pattern as other diabetes types: the better the control and blood pressure, the better the outlook.
Families often want to know how life will change as children with MODY 1 grow up; with regular monitoring, healthy routines, and the right medicine plan, school, sports, travel, and pregnancy are all achievable goals. Talk with your doctor about what your personal outlook might look like, including how often to screen the eyes, kidneys, feet, and heart, and whether genetic testing in relatives could guide care.
Long-term effects
Maturity-onset diabetes of the young type 1 (MODY1) can change gradually over years, shaping eye, kidney, nerve, and heart health if blood sugar stays high. While early symptoms of Maturity-onset diabetes of the young type 1 can be mild, the long-term picture depends on glucose patterns over time. Long-term effects vary widely, and many living with MODY1 do well with careful monitoring. Some features are unique in families with this condition, such as patterns seen during pregnancy and in newborns.
Over time the pancreas may make less insulin. This can mean higher glucose levels and the need for treatment changes.
High glucose over years can injure the retina at the back of the eye. This may lead to blurred vision or vision loss if not detected early.
Persistent high sugar can damage small kidney filters. This can first show up as protein in urine and may progress to kidney disease.
Long-standing high glucose can affect nerves in the feet and hands. People may notice tingling, numbness, or burning pain.
How is it to live with Maturity-onset diabetes of the young type 1?
Living with maturity-onset diabetes of the young type 1 (MODY 1) often means learning a steady rhythm of checking blood sugar, taking medication as prescribed, and planning meals and activity with a bit more intention, while still doing the things you enjoy. Because MODY typically starts at a young age and runs in families, daily choices can ripple through the household—parents, partners, and siblings may share meal planning, reminder routines, or genetic conversations together. Many find that using glucose meters or continuous monitors, keeping snacks handy, and having a clear plan for exercise or busy days turns uncertainty into confidence. Over time, most people fold these habits into everyday life, balancing health needs with school, work, travel, and relationships.
Treatment and drugs
Treatment for Maturity-onset diabetes of the young type 1 (MODY 1) focuses on keeping blood sugar in a healthy range and preventing long-term complications. Many people with MODY 1 respond well to a class of medicines called sulfonylureas, which help the pancreas release more insulin; others may need metformin or, less often, insulin, depending on blood sugar patterns, age, pregnancy, or other health factors. Doctors sometimes recommend a combination of lifestyle changes and drugs, with balanced meals, regular physical activity, and weight maintenance supporting medication effects. Regular checks of A1C, home glucose monitoring, and occasional dose adjustments help fine‑tune control over time. Ask your doctor about the best starting point for you, especially if a genetic test has confirmed MODY 1, since matching treatment to the specific subtype can improve results.
Non-drug treatment
For many living with Maturity-onset diabetes of the young type 1 (MODY1), day-to-day routines can help steady blood sugar and reduce swings that sap energy. Alongside medicines, non-drug therapies often lay the foundation for long-term health. Knowing the early symptoms of Maturity-onset diabetes of the young type 1—like thirst, frequent urination, or unexpected tiredness—can prompt earlier lifestyle steps and monitoring. These approaches are flexible so you and your care team can tailor them to your goals and life stage.
Aim for regular meals with fiber-rich carbs, lean proteins, and healthy fats to smooth post-meal spikes. Consistent timing can make blood sugars more predictable.
Moderate exercise, like brisk walking or cycling, improves insulin sensitivity and lowers glucose. Try for most days of the week, adjusting intensity to your fitness and glucose trends.
Checking glucose before and after meals shows how food, stress, and activity affect you. A continuous glucose monitor (CGM) can reveal patterns and guide small adjustments.
Working with a diabetes educator builds practical skills for meals, activity, and monitoring. Structured programs, like diabetes self‑management education, can help you problem‑solve day to day.
Your genes may have an impact on how drugs work for you
Genes can affect how people with maturity‑onset diabetes of the young type 1 (MODY1) respond to diabetes drugs, including how well they work and the risk of side effects. Specific MODY1 variants may guide choices, like favoring certain oral agents over insulin.
Pharmacological treatments
Treatment for Maturity-onset diabetes of the young type 1 focuses on medicines that help the pancreas release insulin effectively, with choices tailored to your glucose patterns and life stage. Because many are diagnosed after early symptoms of Maturity-onset diabetes of the young type 1 like frequent urination and increased thirst, clinicians often start with drugs that boost the body’s own insulin release. Not everyone responds to the same medication in the same way. Your plan may change over time, especially during pregnancy or if blood sugars rise despite tablets.
Gliclazide, glipizide, or glyburide often work well in MODY type 1 because the pancreas is very responsive to these drugs. First-line medications are those doctors usually try first, based on strong experience in this condition. Low blood sugar can happen, so doses are typically lower than in type 2 diabetes.
Insulin is used if tablets aren’t enough, during pregnancy, or if blood sugars are very high. Sometimes medicines are taken short-term (acute treatment), while others are used long-term (maintenance therapy). Your team will adjust doses gradually to reduce low blood sugars.
Repaglinide or nateglinide can help control mealtime spikes by prompting a short burst of insulin. They may suit people with MODY type 1 who get low blood sugar on sulfonylureas or need flexible dosing around meals. Hypoglycemia can still occur, but often for a shorter time.
Metformin is not the primary drug in MODY type 1, but it can be added if there’s insulin resistance or weight gain. It lowers glucose made by the liver and rarely causes low blood sugar. Stomach upset is the most common side effect and often improves when taken with food.
Genetic influences
Diabetes that starts young and appears in several generations can be a clue to a genetic form. Maturity-onset diabetes of the young type 1 (often called MODY1) usually stems from a change in a gene named HNF4A, which influences how the pancreas makes and releases insulin. Family history is one of the strongest clues to a genetic influence. If a parent has MODY1, each child has a 50% chance of inheriting the same gene change, but the age it appears and how strongly it affects blood sugar can vary within the family. A genetic test can often confirm an HNF4A change, and some relatives may have mild or later-onset features while others need treatment sooner. Occasionally, the gene change arises for the first time in a child, so there may be no family pattern to point to. Knowing this inheritance pattern can guide testing and care plans, and help you watch for early symptoms of Maturity-onset diabetes of the young type 1.
Is Maturity-onset diabetes of the young type 1 genetic?
Genetics is central in Maturity-onset diabetes of the young type 1 (MODY1). Single inherited variants in the HNF4A gene typically cause it, following an autosomal dominant pattern. One altered copy often leads to MODY1, with strong family clustering.
Pharmacogenetics—how genetics influence drug effects
For many living with Maturity-onset diabetes of the young type 1 (MODY1), the specific gene change helps guide which diabetes medicines work best and at what dose. Alongside medical history and blood-sugar patterns, genetic testing can help tailor treatment by confirming MODY1 and pointing to options that may work with fewer side effects. People with MODY1 often respond strongly to sulfonylureas, so doctors may try a lower dose than usual or even switch from insulin, with close monitoring to avoid low blood sugar. Response isn’t only about genes—age, pregnancy, kidney or liver health, and other medicines also matter. During pregnancy, treatment plans for MODY1 may shift because some diabetes pills can reach the baby; insulin is often favored to keep both parent and baby safe. If sulfonylureas aren’t a good fit, other options such as metformin or certain newer injectables may be considered, though evidence in MODY1 is more limited and dosing still needs to be individualized.
Interactions with other conditions
Living with Maturity-onset diabetes of the young type 1 can feel different when another health issue is in the mix. Doctors call it a “comorbidity” when two conditions occur together. Extra insulin resistance from overweight, polycystic ovary syndrome, or inactivity can make blood sugars swing higher and make tablets like sulfonylureas less predictable. High blood pressure and unhealthy cholesterol levels can add to the risk of heart, eye, kidney, and nerve problems over time, so treating these alongside MODY1 is just as important as glucose control. MODY1 itself isn’t an autoimmune condition, but if autoimmune thyroid disease or celiac disease is also present, it can blur the picture and sometimes delay the right diagnosis and treatment. Pregnancy needs special planning: HNF4A changes can lead to larger babies and low blood sugar in newborns, so coordinated obstetric and diabetes care helps keep both parent and baby safe. Illnesses or treatments for other conditions—especially infections or steroid medicines—can temporarily raise glucose, so let your care team know and ask how to adjust your plan when that happens.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described families where several members developed high blood sugar at a young age but did not fit the usual patterns of type 1 or type 2 diabetes. A teenager might have been told they had “mild diabetes,” needing only small doses of insulin or tablets, while a parent and grandparent shared similar stories. Doctors noticed these patterns long before lab tests could explain them.
From early written records to modern studies, the picture gradually sharpened. Mid-20th-century clinicians reported “familial, early-onset diabetes” that seemed stable and often didn’t require insulin right away. In the 1970s and 1980s, careful family mapping and glucose testing showed a distinct inheritance pattern, often appearing in each generation. Researchers proposed a group of conditions they called maturity‑onset diabetes of the young, or MODY, to capture this cluster of features.
Building on this early work, scientists turned to genetics in the 1990s. They discovered that different single-gene changes could cause different MODY types. One of the earliest and most influential findings involved a gene that acts like a glucose sensor in insulin‑producing cells. Changes in this gene led to a very specific form, now known as MODY type 1 (also called HNF4A‑MODY), which often runs strongly in families and can respond well to certain oral medicines.
As medical science evolved, naming and grouping also shifted. MODY type 1 became linked to its gene cause, helping doctors predict features such as age at diagnosis, likelihood of needing insulin over time, and which treatments might work best. This genetic clarity separated Maturity‑onset diabetes of the young type 1 from other MODY forms, each tied to a different gene and clinical pattern.
In recent decades, awareness has grown as genetic testing became more available in clinics. People with Maturity‑onset diabetes of the young type 1 could finally receive a precise diagnosis, rather than being labeled with type 1 or type 2 diabetes. That accuracy matters: it guides treatment, informs screening of relatives, and reduces uncertainty. Understanding has deepened further as registries in Europe and the United States collected data, revealing both the common threads—strong family history, early-onset hyperglycemia—and the variability in symptoms and treatment needs.
Knowing the condition’s history helps explain today’s approach: combine family clues with targeted genetic testing to confirm the diagnosis and tailor care. What began as a set of careful observations in families has become a clear, gene‑based diagnosis that supports more personal, effective treatment for people living with Maturity‑onset diabetes of the young type 1.