Adult-onset
Type 1 diabetes is simply Type 1 diabetes with new-onset at about age 20 or
older. Most cases of Type 1 diabetes are
autoimmune in nature, resulting from immune-mediated destruction of the beta
cells of the pancreas. Markers for the
immune-mediated destruction of the beta cells include autoantibody markers glutamic acid decarboxylase autoantibodies (GAD),
islet cell cytoplasmic autoantibodies (ICA), insulinoma-associated 2
autoantibodies (IA-2), insulin autoantibodies (IAA), and zinc transporter 8
autoantibodies (ZnT8). Other
autoantibodies may exist but have not yet been discovered. Type 1 diabetes is associated with HLA DR3/4
genes. People with Type 1 diabetes
require exogenous insulin for survival.
Type 1 diabetes was previously called juvenile diabetes, and the myth
that Type 1 diabetes is a childhood disease creates significant problems for
those diagnosed as adults. The truth is
that Type 1 diabetes can be diagnosed at any age and adult-onset Type 1 diabetes far outnumbers childhood-onset Type 1 diabetes.
Adults with
new-onset Type 1 diabetes frequently experience the problem of incorrect or
delayed diagnosis which results in needless human suffering and can result in
the rapid onset of diabetic complications and even death due to diabetic
ketoacidosis (DKA). New-onset Type 1
diabetes in adulthood [Footnote 1] is far more prevalent than childhood-onset Type 1 diabetes [Footnote 2],
but the myth that Type 1 diabetes is a childhood disease and the rising
epidemic of Type 2 diabetes often means that adults with new-onset Type 1
diabetes are incorrectly diagnosed as having Type 2 diabetes, an altogether
different disease. Patients who are
misdiagnosed and treated as if the patient has Type 2 diabetes are often
undertreated with medications that do not help their medical condition. As stated in a Wall Street Journal article on the problem of misdiagnosis (“Wrong
Call: The Trouble Diagnosing Diabetes,” August 2012), "Most of my [adult Type 1 patients] have been misdiagnosed as
having Type 2," says Robin Goland, co-director of the Naomi Berrie
Diabetes Center at Columbia University Medical Center in New York. "Once
the right diagnosis is made the patient feels much, much better, but they are
distrustful of doctors and who could blame them?"
In 2016, the American Association of Clinical Endocrinologists (AACE) stated that Type 1 diabetes should be confirmed by the presence of autoantibodies, to distinguish between T1D and T2D and determine appropriate treatment. Dr. David
Bell suggests that autoantibody testing assists with identifying the type of
diabetes, guiding the clinician to appropriate treatment with insulin, avoiding
a period of poor glycemic control when oral therapy [medications for Type 2
diabetes] is failing, optimizing the potential for preservation of beta cell
function, and maximizing the prevention of long-term complications of diabetes.
Well-known
people who were diagnosed with Type 1 diabetes as adults include actress Mary
Tyler Moore (diagnosed at age 33), former acting Surgeon General Dr. Kenneth
Moritsugu (age 49), UK Prime Minister Theresa May (age 56), and Olympic swimmer (10 Olympic medals) Gary Hall, Jr. (age
24).
Footnote 1: Type 1 diabetes in
adults can be acute onset or slowly progressive. Slowly progressive Type 1 diabetes is sometimes
called latent autoimmune diabetes in adults (LADA) or Type 1.5 diabetes. More recently, diabetes researchers have
discouraged the use of the term latent autoimmune diabetes in adults, because
LADA is not a latent disease.
Footnote 2: The U.S. Centers for
Disease Control and Prevention’s (CDC’s) most current information on the
prevalence and incidence of Type 1 diabetes comes from Diabetes in America, Chapter 3, “Prevalence and Incidence of
Insulin-Dependent Diabetes” (Diabetes in
America, Second Edition, 1995).
Although people who use that reference as a source of incidence
statistics state that there are about 30,000 new cases of Type 1 diabetes each
year and that half of those cases are children; in fact, that source states
that children (<20 years of age) account for 13,171 cases and adults (>20
years of age) account for 16,542 cases, for a total of 29,713 new cases of Type
1 diabetes per year, 56% seen in adults.
Furthermore, that source states that there is an unknown number of
adults identified as having Type 2 diabetes who have slowly progressive Type 1
diabetes (Michael J. Haller MD, in Type 1 Diabetes Sourcebook (ADA/JDRF,
2013), says “Importantly, adults with LADA may represent an additional 10% of
those adults incorrectly diagnosed with
Type 2 diabetes.”) The number of
people with slowly progressive Type 1 diabetes is quite large, consistently
about 10% of “Type 2” diabetes based on autoantibody testing (for example, the
first study that demonstrated that about 10% of people with “Type 2” diabetes
are autoantibody positive was published in The
Lancet in 1977. In the UKPDS, about
10% of people diagnosed with “Type 2” diabetes were autoantibody positive and
had been misdiagnosed). Clinicians use autoantibody tests to distinguish between
Type 1 autoimmune diabetes and non-autoimmune diabetes (Type 2 diabetes,
monogenic diabetes, etc.).
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