The familiar type 2 case that turns out to be slow type 1 diabetes

Consider a patient doctors see again and again. In this teaching case, recounted by Dr. Adam Brockman as a composite built from a familiar pattern, she is 44, slim, active, and cooks at home. During an ordinary physical, lab work finds elevated blood sugar, and a test called A1C, which reflects average blood sugar over months, comes back firmly at a diabetes level.

The physician in the scenario settles on the expected diagnosis: type 2 diabetes. She starts the drug metformin, cuts carbs, and walks daily. At first, the plan appears to work. She tightens her diet, her numbers improve, and the label sticks.

That label is the problem. Brockman says the case illustrates a slow form of type 1 diabetes that arrives in adulthood, and an estimated 4 to 12 percent of adults told they have type 2 actually have this condition.

About 18 months after the diagnosis in the case file, the turn comes. She is thirsty all the time, up at night to use the bathroom, and exhausted. She loses 15 pounds without trying, a frightening drop for someone already slim. Her A1C keeps climbing even though she follows the plan, so a second drug is added, then a third.

In the scenario, her doctor openly questions whether she is truly following the eating plan. She heads home feeling at fault, and late at night she searches through everything she can and wonders whether she is somehow broken.

Three clues point elsewhere. Her mother lives with an autoimmune thyroid disorder, her sister with celiac disease, in which the immune response reacts to gluten, and her own blood sugar keeps rising while her weight keeps falling.

The answer in the case is LADA, short for latent autoimmune diabetes in adults and sometimes called type 1.5. Two blood tests can separate it from type 2, one that looks for GAD antibodies that signal an immune attack and one called C-peptide that gauges how much insulin output remains. Like childhood type 1, LADA is an immune attack on the insulin-making cells in the pancreas. In adults, that attack can move slowly. For a while enough insulin remains that diet changes and pills seem to help, until the cells fade and insulin falls and, as he says, "no pill can fix a factory that is closed."

For the woman in the case file, the first blood sugar result was not wrong, only the interpretation. Once LADA is found, insulin is the treatment that replaces what the pancreas no longer makes, and, as Dr. Adam Brockman says, "most people with LADA eventually need insulin sometime within months, sometimes within a few years."