Johns Hopkins experts explain the difference between type 2 diabetes and Latent Autoimmune Diabetes of Adulthood (LADA).

Not so long ago, a patient’s age was a near-perfect predictor of which type of diabetes to diagnose. People under age 30 usually had type 1 diabetes (which is why it used to be called juvenile diabetes), and people who developed diabetes after age 30 had type 2 disease.

That all changed with the sudden rise of type 2 diabetes among young people in the United States during the last decade or so. Now researchers are also identifying more new cases of type 1 diabetes in adults, which was once considered rare. This adult-onset form of type 1 diabetes is known by various names, the most common being Latent Autoimmune Diabetes of Adulthood (LADA).

Think of LADA as a slow-moving form of type 1 diabetes: The destruction of insulin-producing beta cells in the pancreas progresses more gradually than in type 1 diabetes.

In fact, people with LADA often initially appear to have type 2 diabetes -- albeit an unusual case. Instead of being overweight and sedentary, many are slender and active. They also have little or no insulin resistance, the hallmark of type 2 diabetes. But like type 2 diabetes patients, those with LADA have some remaining healthy beta cells -- at least to begin with. That’s why initially they can keep their blood glucose under control with diet and oral medications. But within a few years, most lose the ability to produce insulin. The typical person with LADA requires insulin injections far sooner than the average person with type 2 diabetes.

Research suggests that a surprising number of people diagnosed with type 2 diabetes may actually have the adult-onset variety of type 1 diabetes. One way to determine the type of diabetes a person has is to measure blood levels of pancreatic antibodies, proteins that attack the insulin-making beta cells in the pancreas. People who test positive for these antibodies usually have inflamed pancreatic islets, which is a sign of type 1 diabetes.

A study of more than 3,600 adults in the United Kingdom who had been diagnosed with type 2 diabetes found that one in 10 had pancreatic antibodies in their blood. The study also found that about 90% of participants who had the antibodies needed insulin therapy within six years, compared with just 14% of the people who tested negative for the antibodies.

Knowing whether you have LADA or type 2 diabetes is important, since management of the two conditions differs. For instance, type 1 diabetes that begins at any age requires a finely tuned insulin regimen, while people with type 2 diabetes sometimes do not need insulin at all or, when they do, may need injections just once per day.

A team of Australian physicians recently developed a screening system that may help doctors suspect LADA. They found that, compared with people with type 2 diabetes, LADA patients were more likely to have at least two of the following traits:

• Younger than age 50 at diabetes diagnosis
• Normal weight (a body mass index less than 25)
• Acute symptoms (such as extreme thirst, frequent urination, or unintentional weight loss) when diagnosed with diabetes
• A personal history of another autoimmune disease, such as autoimmune thyroid disease, rheumatoid arthritis, or celiac disease
• A family history of type 1 diabetes or other autoimmune diseases.