Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 78-year-old woman who resides in a nursing home is seen for management of her diabetes mellitus. The patient’s blood glucose log shows levels ranging between 40 and 400 mg/dL (2.2 and 22.2 mmol/L). She otherwise feels well. She has been on insulin for more than 25 years after first taking oral agents for several years following her initial diagnosis. The patient has hypothyroidism treated with levothyroxine and remote history of Graves disease treated with radioactive iodine. Her diabetes is currently treated with neutral protamine Hagedorn (NPH) insulin, 25 units twice daily; the dosage has been gradually increased over the past 3 weeks.
The only pertinent finding on physical examination is her lean body habitus (BMI of 19.3 kg/m2).
Results of routine laboratory studies are all within the normal range. An anti-glutamic acid decarboxylase antibody titer is positive.
Which of the following is the most likely diagnosis?
A) Late-onset autoimmune diabetes of adulthood
B) Maturity-onset diabetes of the young
C) Type 1 diabetes mellitus
D) Type 2 diabetes mellitus
MKSAP Answer and Critique
The correct answer is A) Late-onset autoimmune diabetes of adulthood. This item is available to MKSAP 15 subscribers as item 2 in the Endocrinology and Metabolism section. More information about MKSAP 15 is available online.
This patient most likely has late-onset autoimmune diabetes of adulthood (LADA). Diabetes mellitus is categorized into several types. Most affected patients have type 2 diabetes, and a minority (5% to 10%) have type 1 diabetes. Patients with type 2 diabetes are usually overweight, if not frankly obese. Type 1 diabetes results from autoimmune destruction of pancreatic beta cells and results in absolute insulin deficiency, whereas type 2 is marked by insulin resistance and relative insulin deficiency. Type 1 diabetes is classically seen in younger patients, usually in children, teens, and young adults. However, type 1 diabetes can be diagnosed at any age. When diagnosed in older persons, especially those in whom hyperglycemia was once controlled with oral agents, this form of diabetes is referred to as LADA. In persons with LADA, beta cell destruction over time leads to the requirement for insulin therapy, as in type 1 diabetes. LADA typically occurs in leaner persons after glycemic control has become more labile and there is clear insulin dependency. Autoimmune markers (anti-islet cell autoantibodies) are present, including anti-glutamic acid decarboxylase antibody, the detection of which can confirm the diagnosis.
Maturity-onset diabetes of the young is typically diagnosed in adolescents or young adults and usually is marked by mild hyperglycemia, often with a strong family history of diabetes.
Key Point
- Diabetes mellitus in older, lean patients with anti-islet cell autoantibodies is termed late-onset autoimmune diabetes of adulthood.
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