Maturity onset diabetes of the young (MODY)
Q: What is MODY?
MODY is a rare form of diabetes which is different from both Type 1 and Type 2 diabetes, and runs strongly in families.
Q: What causes MODY?
MODY is caused by a mutation (or change) in a single gene. If a parent has this gene mutation, any child they have, has a 50% chance of inheriting it from them. If a child does inherit the mutation, they will generally go on to develop MODY before they’re 25, whatever their weight, lifestyle, ethnic group etc.
Q: What are the features of MODY?
The key features are:
- Being diagnosed with diabetes under the age of 25.
- Having a parent with diabetes, with diabetes in two or more generations.
- Not necessarily needing insulin.
Q: How common is MODY?
MODY is very rare compared with Type 1 and Type 2 diabetes – experts estimate that only 1-2% of people with diabetes (20-40,000 people) in the UK have it. But because MODY is so rare, doctors may not be aware of it, so it’s estimated that about 90% of people with it are mistakenly diagnosed with Type 1 or Type 2 diabetes at first.
Q: Are there different types of MODY?
Yes, mutations in several different genes can cause MODY. The most common types of MODY are:
- HNF1-alpha. This gene causes about 70% of cases of MODY. It causes diabetes by lowering the amount of insulin made by the pancreas. In childhood you generally make enough insulin to cope with your body’s needs, but the amount of insulin you make reduces as you get older. So diabetes usually develops in adolescence or early twenties, but may not be diagnosed until later in life. People with HNF1-alpha MODY generally don’t need to take insulin, and can be treated with small doses of a group of tablets called sulphonylureas (often used in Type 2 diabetes). As with Type 1 and Type 2 diabetes, you should also follow a healthy balanced diet and keep physically active as this also helps to maintain good blood glucose and cholesterol levels. Good control of blood glucose and cholesterol levels are important in HNF1-alpha as it has the same risk of complications as Type 1 and Type 2 diabetes.
- Glucokinase. This gene helps the body to recognise how high the blood glucose level is in the body. When this gene isn’t working properly the body allows the level of blood glucose to be higher than it should be. Blood glucose levels in people with glucokinase MODY are typically only slightly higher than normal, generally between 5.5-8mmol/l. You don’t generally have symptoms of this type of MODY and so it’s often picked up through routine testing (eg during pregnancy). You don’t need any treatment for glucokinase MODY and it’s rare to get any of the complications of diabetes.
- HNF4-alpha. This isn’t as common as the other forms of MODY. People who have inherited a change in this gene are likely to have had a birth weight of 9lb or more (around 4 kg). They may also have had a low blood sugar at, or soon after, birth which might have needed treatment. Early after diagnosis people with HNF4-alpha are generally treated with a sulphonylurea tablet but may progress on to needing insulin. You should also follow a healthy balanced diet and keep physically active as this also helps to maintain good blood glucose and cholesterol levels. Good control of blood glucose and cholesterol levels are important in HNF4 -alpha as it also carries a risk of the complications of diabetes.
- HNF1-beta. People with this type of MODY can have a variety of problems including renal cysts (cysts of the kidneys), uterine abnormalities and gout as well as diabetes. Often the renal cysts can be detected in the womb before a baby is born. The diabetes tends to develop later and insulin treatment is usually necessary, as well as following a healthy balanced diet and getting regular physical activity. HNF4-beta MODY also carries a risk of complications of diabetes.
Q: What should I do if I think I’ve got MODY?
It’s important to know if you’ve got MODY, for the following reasons:
- To make sure you get the right treatment and advice for your type of diabetes (eg stopping insulin).
- As there is a 50% chance of a parent passing on MODY to their child, you can consider and discuss the risk to any children you have/plan to have.
- Genetic testing can be offered to other family members.
So if you think you have the features of MODY, you should discuss testing with your doctor. Testing usually involves:
- Having blood taken for pancreatic antibodies (your doctor/hospital can do this).
- Having a blood/urine test for C-peptide levels which tells whether your body is making any insulin (though if you have Type 1 diabetes, this test isn’t particularly helpful as you can still make some of your own insulin for up to 5 years after you were diagnosed).
- Having blood taken for genetic testing. Your doctor/hospital will take the blood from you, but they will send it on to the specialist centre in Exeter for it to be tested, along with details of your diagnosis and treatment.
Q: Where can I go for more information?
Go to www.diabetesgenes.org. This site will give you lots of information including:
- More detail about MODY and genetic testing.
- Details of research that’s being done into MODY.
- Information about regional Genetic Diabetes Nurses who work around the country to provide local support for people with MODY.
Reference:
Shepherd M.(2011) How do I know if I’ve got MODY? Diabetes Wellness News 13 (7) pages 4-5