Interactive diabetes case 4: Uncontrolled diabetes in a 51-year-old patient on insulin and two oral agents – Comment

Comment — Up to 10 percent of adult patients who are initially classified as having type 2 diabetes are later found to have latent autoimmune diabetes in adults (LADA) based on the presence of anti-islet antibodies. Thus, phenotype is not a precise guide to the etiology of diabetes mellitus. (See "Classification of diabetes mellitus and genetic diabetic syndromes", section on 'Latent autoimmune diabetes in adults (LADA)'.)

This condition should be considered when the patient:

●Develops diabetes at age <50 years

●Presents with symptoms of polyuria, polydipsia, and nocturia and with weight loss in the absence of ketoacidosis

●Fails to respond, or responds for only a few months or years, to oral agents for the treatment of diabetes

●Lacks other features of the metabolic syndrome, such as obesity, hypertension, and hyperlipidemia

●Requires insulin doses that are below those expected for a patient with type 2 diabetes (0.6 to 1 unit/kg body weight)

●Exhibits lability of blood glucose levels not explained by variations in diet or physical activity

●Has a personal or family history of autoimmune disease

Because both type 1 and type 2 diabetes are common disorders, one may encounter patients with features of both type 1 and type 2 diabetes, as in the present case. Patients who present with the phenotype of type 2 diabetes and have a family history of both type 1 and type 2 diabetes or islet antibodies have, in the aggregate, a phenotype that is intermediate between patients with classical type 1 diabetes and those with type 2 diabetes. Patients with LADA share genetic features of both type 1 and type 2 diabetes, consistent with the view that LADA is an admixture of the two main types of diabetes. (See "Classification of diabetes mellitus and genetic diabetic syndromes", section on 'Latent autoimmune diabetes in adults (LADA)' and "Classification of diabetes mellitus and genetic diabetic syndromes", section on 'Distinguishing type 1 from type 2 diabetes'.)

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