- Neonatal diabetes - diabetes is diagnosed before six months of age.
- Familial diabetes - (also known as maturity onset diabetes of the young or MODY).
This type of diabetes is diagnosed within the first six months of life. It may last for a short time then resolve but return again, typically during the teenage years, or be permanent. The features of the condition include low birth weight, undetectable pancreatic autoantibodies (proteins made by the immune system which attacks the body's own tissue) and marked hyperglycaemia (high levels of glucose in the blood) at diagnosis.
Around 50 to 60 per cent of those with permanent neonatal diabetes have been identified with changes in one of the potassium channel genes (Kir6.2 or SUR1), which affects insulin production. Ninety per cent of these patients have been able to stop insulin treatment and transfer to high doses of sulphonylurea tablets which enables their body to secrete their own insulin and therefore better control the glucose level in their blood. Twenty per cent of patients with changes in Kir6.2 or SUR1 also have neurological features such as delayed development (see entry Global Developmental Delay) and epilepsy which is associated with their diabetes.
Familial diabetes (MODY)
MODY is passed down from an affected member in one generation to the next (it is inherited). The change in the gene is inherited from an affected parent, therefore diabetes is present in two or more generations. Each child has a 50 per cent chance of inheriting the affected gene from their parent with MODY and if they inherit the affected gene their lifetime risk of developing diabetes is greater than 99 per cent. Familial diabetes is typically diagnosed before 25 years of age in at least one family member. People with MODY continue to make insulin of their own, but due to the young age of diagnosis are often mistaken to have Type 1 diabetes and unnecessary started on insulin.
HNF1A accounts for 60 per cent of UK MODY. Additional features include a low level at which the kidneys allow glucose into the urine (renal threshold) and sulphonylurea sensitivity. Patients with HNF1A diabetes are known to be particularly sensitive to tablets called sulphonylureas, which help the body produce more insulin and this is considered the most appropriate form of treatment for this group. Annual screening for complications is advisable. HNF1A diabetes is progressive, gets worse over time, and although HNF1A diabetes can often be managed with sulphonylurea tablets for many years, the addition of insulin may be required in middle/later life.
HNF4A is rarer than HNF1A, but has similar features although age of diagnosis of diabetes may be later. Those affected tend to have high birth weight (above 4kg/9lb) and may have low blood glucose shortly after birth, which may require treatment. Patients with HNF4A can also be managed on sulphonylurea tablets for many years.
GCK accounts for 22 per cent of UK MODY. It is characterised by mild, stable raised blood glucose throughout life. The condition is often detected by routine screening. No treatment is required and complications are rare.
In HNF1B MODY, renal (kidney) cysts (or other kidney problems) are often present and may be detected during antenatal ultrasound. Gout can also occur. Diabetes may become apparent after the renal problems. This condition usually requires treatment with insulin.