Latent autoimmune diabetes in adults: definition, prevalence, beta-cell function, and treatment.

Latent autoimmune diabetes in adults (LADA) is a disorder in which, despite the presence of islet antibodies at diagnosis of diabetes, the progression of autoimmune beta-cell failure is slow. LADA patients are therefore not insulin requiring, at least during the first 6 months after diagnosis of diabetes. Among patients with phenotypic type 2 diabetes, LADA occurs in 10% of individuals older than 35 years and in 25% below that age. Prospective studies of beta-cell function show that LADA patients with multiple islet antibodies develop beta-cell failure within 5 years, whereas those with only GAD antibodies (GADAs) or only islet cell antibodies (ICAs) mostly develop beta-cell failure after 5 years. Even though it may take up to 12 years until beta-cell failure occurs in some patients, impairments in the beta-cell response to intravenous glucose and glucagon can be detected at diagnosis of diabetes. Consequently, LADA is not a latent disease; therefore, autoimmune diabetes in adults with slowly progressive beta-cell failure might be a more adequate concept. In agreement with proved impaired beta-cell function at diagnosis of diabetes, insulin is the treatment of choice.

HLA-DQ genotypes in classic type 1 diabetes and in latent autoimmune diabetes of the adult.

In 1993-1996, islet autoantibodies, C-peptide, and HLA-DQ genotypes were evaluated in 345 insulin-treated diabetic patients of all ages from the Skaraborg Diabetes Registry 5-6 years after their diagnosis and in 216 control subjects from the Skaraborg County, Sweden, population. The aims of this study were to clarify the importance of age at diagnosis of diabetes for HLA-DQ associations in patients with classic type 1 diabetes and whether patients considered to have latent autoimmune diabetes of the adult differed in their human leukocyte antigen (HLA) associations. An abnormally low fasting C-peptide value was used as the definition of type 1 diabetes, found in 182 of 345 (53%) patients. No major associations between age at diagnosis and HLA susceptibility or protective genotypes were detected in type 1 diabetic patients. Among the 163 patients with preserved beta-cell function, the frequency of HLA protective genotypes was clearly decreased (5% vs. 42%) in the 46 of 163 with islet antibodies compared with the 117 of 163 antibody-negative patients. The authors conclude that there were no major effects of age at diagnosis on HLA-DQ associations in classic type 1 diabetic patients, whereas lack of HLA-DQ protective genotypes was a feature of patients with slow-progressing type 1 diabetes (latent autoimmune diabetes of the adult).