A 16-year-old girl went to her pediatrician for her annual visit and complained of being very tired for a while. Despite this, she just completed 10th grade with minimal absences.

She has a history of obesity, weighing as much as 230 pounds on a 5-foot-3 frame. But in the last year, she devoted herself to improved nutrition and exercise.  She stopped drinking sweetened sodas in favor of lots of water.

Her parents agree that her diet has been healthier, but think her exercise has been minimal.

Both the pediatrician and family were happy to learn that over the last six months, her weight decreased to 205 pounds.  But she can't understand why, despite her healthier lifestyle, she feels so tired.

Fatigue is one of the most difficult complaints to sort out because it is found in so many teens.

Some reports cite that 40 percent of healthy teens experience regular sleepiness and 30 percent fatigue (perception of low energy after normal activity). Causes can include infection (mononucleosis, for example), anemia (low red blood cells), hypothyroidism, sleep disorders, and depression.

In this case, the pediatrician asked her many questions.  She denied fever or sore throat (mono), trouble sleeping (obstructive sleep apnea), bleeding such as heavy periods (that might lead to an anemia), and she denied a history of depression.  The girl's mother reported she was diagnosed with hypothyroidism in her 20s.  Hypothyroid symptoms might include fatigue and sleepiness, weight gain, dry skin, constipation, irregular menstrual cycles, feeling cold, and an enlarged thyroid.  But the girl said she had none of these symptoms except for fatigue and some sleepiness.

She said that her only sleep problem is needing to get up in the night to urinate – but she attributed this to all the water she was drinking as part of her healthier lifestyle.

Examining her, the doctor noticed that the skin behind her neck was dark. Her mother said she'd tried scrubbing numerous times, but to no avail. The doctor recognized the condition as acanthosis nigricans, a skin disorder associated with insulin resistance and Type 2 diabetes. Further, he discovered that a rash in her groin area was a yeast infection, a condition that thrives in moist areas of the body, especially when blood sugars are elevated.

The physician ordered blood tests. She didn't have anemia, and thyroid function was normal. Her non-fasting blood glucose was 190 mg/dL and a hemoglobin A1c of 6.4 percent. She was right on the line: A blood glucose above 200 mg/dL with symptoms would establish a diagnosis of diabetes mellitus.  So would a reading above 6.4 on her hemoglobin A1c, a blood test that correlates with the average blood glucose over the last two to three months.

She was sent to a pediatric endocrinologist six weeks later with the diagnosis of pre-diabetes, acanthosis nigricans, yeast infection, and obesity.  This time, her blood glucose reading was 314 mg/dL, and the hemoglobin A1c was 7 percent.

The pediatric endocrinologist learned that a grandmother was recently diagnosed with type 2 diabetes.

Did this teen also have type 2 diabetes?

Solution:

The diagnosis is clearly diabetes mellitus in a child with insulin resistance and obesity.  Type 2 diabetes typically presents over months and does not usually need urgent treatment, which seemed to be the case for this patient.

But the endocrinologist didn't stop there.  Knowing the girl's mother has a history of hypothyroidism (Hashimoto's thyroiditis), an autoimmune condition helped raise the possibility that the girl really could have Type 1 diabetes, also an autoimmune disease.

When a child – especially an overweight teenager — presents with new onset diabetes, it can be difficult to decide immediately which type of diabetes is present.  If a child is under age 6 or is very thin, type 1 diabetes is likely.  If a child is severely ill and in "diabetic ketoacidosis" then type 1 is also likely.

When a child is in puberty, such as this patient, the insulin needs are greater, which explains why type 2 diabetes may develop in a child whose insulin needs are additionally elevated because of factors such as obesity and heredity.

Type 2 diabetes is more common in blacks, Hispanics and Native Americans.  A family history of diabetes is more common with type 2 than type 1.

The girl was started on insulin. A week later, a blood test — the autoimmune diabetes panel — showed elevated diabetes antibodies.

So she did, in fact, have type 1 diabetes.  The acanthosis nigricans suggests that her insulin levels were elevated previously, indicating perhaps a risk for both types of diabetes.

This case illustrates that despite the obesity epidemic increasing the risk of type 2 diabetes in children, clinicians must consider that an obese child with pre-diabetes (elevated glucoses but not quite in the diabetic range), may actually have type 1 diabetes.

This matters a great deal because in type 1, the body destroys its own insulin-producing beta cells. Type 2, however, is a metabolic disorder, not an autoimmune disease. In type 2, insulin resistance develops. So if this girl had been treated for type 2, she would likely have not been given as aggressive insulin therapy, and been at risk for a condition called diabetic ketoacidosis (DKA).  DKA is a condition that can be deadly but is rarely seen in those with type 2 diabetes.

Craig A. Alter, M.D., is a pediatric endocrinologist and director of the Pituitary Center in the Division of Endocrinology and Diabetes at Children's Hospital of Philadelphia. Lorraine L. Katz, M.D., is an attending physician at Children's Hospital of Philadelphia who cares for children with diabetes, hyperinsulinism, and other endocrine disorders.