What’s in a Name

Latent autoimmune diabetes of adults, type 1.5, adult-onset, and type 1 diabetes

Shortly after the original description of islet cell antibodies (ICAs) as a marker for childhood type 1 diabetes, it was realized that some adult-onset patients are also ICA positive (1). With the discovery of GAD antibodies as another marker of type 1 diabetes, Paul Zimmet et al. (2) introduced the term “latent autoimmune diabetes of adults” (LADA) to describe an important minority of adult-onset patients with diabetes. Typical patients are positive for GAD antibodies, 35 years of age or older, nonobese, and present without ketoacidosis and weight loss. Although many maintain good glycemic control for several years with sulfonylureas, these patients become “insulin dependent” more rapidly than antibody-negative type 2 diabetic patients (2).

Unfortunately, the phenotype of adult-onset diabetic patients, including their presentation, is extremely variable, resulting in confusion with the nomenclature and classification of these patients. Besides LADA, these patients have been named type 1.5 diabetes, “slowly progressive type 1 diabetes,” “latent type 1 diabetes,” “youth-onset diabetes of maturity,” and even LADA-type 1 and LADA-type 2 (3). How should these patients be classified?

A major question facing the diabetes community is whether all autoantibody-positive diabetes is due to the same pathophysiological disease process. Is autoimmune diabetes in adults due to the same underlying disease process as childhood type 1 diabetes? Or do some patients with autoimmune diabetes in adulthood have a distinct form of autoimmune diabetes compared with classic childhood type 1 diabetes? Phenotypically there are at least three separate populations of autoimmune diabetes in adults: LADA, adult-onset type 1 diabetes, and obese phenotypic type 2 diabetes in patients who are antibody positive.

In this issue of Diabetes Care, Hosszúfalusi et al. (4) compared patients with LADA with patients presenting with classic type 1 diabetes at older ages. These populations were also compared with a control group …