Diagnostic dilemma: A teen's classic diabetes symptoms didn't improve with treatment — revealing she also had a much rarer syndrome

The patient: A 17-year-old girl in California

The symptoms: The teenager went to an emergency department after experiencing vomiting episodes for about a day. Over the prior three months, she'd also had periodic shortness of breath accompanied by tightness in her chest.

What happened next: A test revealed that the patient's blood sugar was very high. It was 25.2 mmol/L (453 milligrams per deciliter (mg/dL)), whereas a normal blood sugar range for someone without diabetes is between 3.9 and 5.5 mmol/L (70 to 90 mg/dL). A hemoglobin A1C test, which measures average blood sugar levels over the past few months, delivered a result of 12%, with anything higher than 6.4% signaling diabetes.

Doctors learned that the patient had also experienced unusual thirst, excessive urination, unexplained weight loss and fatigue. Based on these symptoms and the high blood sugar, the doctors determined the patient likely had type 1 diabetes and admitted her to the pediatric department for further tests.

They started her on a conservative dose of insulin, but despite that, she often experienced low blood sugar in the mornings. And despite low fluid intake, she still urinated a lot, which is a characteristic symptom of uncontrolled diabetes.

The patient's mother also told doctors that the teen generally tended to "tan easily," though she didn't happen to have a tan at the time of the hospitalization.

"Given her atypical course and persistent findings," the doctors began looking into additional diagnoses that might explain these symptoms, they wrote in a report of the case.

The diagnosis: They considered whether the symptoms pointed to Addison's disease, which affects the adrenal glands located above the kidneys. These glands normally produce hormones that help control the stress response, blood pressure and water-salt balance in the body, but in patients with Addison's, they don't make enough of the hormones. This is most often caused by an autoimmune response, in which the immune system attacks the adrenal glands and undermines their function.

Tests showed that the patient carried antibodies against the adrenal glands, suggesting that such an autoimmune response was unfolding. Additionally, she had high levels of adrenocorticotropic hormone (ACTH), a signal the brain sends out in an attempt to crank up the activity of the adrenal glands; and renin, which the kidneys make when the body's water-salt balance is off.

At the same time, the brain also releases more of a hormone that drives up pigmentation in the skin, which can cause it to "tan."

These findings confirmed diagnoses of both type 1 diabetes and Addison's disease. Together, these diseases point to another, relatively rare condition called autoimmune polyendocrine syndrome type 2 (APS-2). This syndrome affects various hormone-making glands and is estimated to affect about 1.5 to 2 in 100,000 people.

The treatment: The patient received both short-acting and long-acting insulin to manage her diabetes. For Addison's disease, she was given a number of steroids to help boost levels of two key hormones: cortisol and aldosterone. These hormones, which are normally made by the adrenal glands, work together to manage blood pressure, fluid balance and stress responses. "This dose [of steroids] has been managing her symptoms well thus far," her doctors wrote.

Within two months of her diagnosis, she had begun gaining weight, her blood sugar levels had improved, and her ACTH and renin levels had normalized.

"Symptomatically, she has improved," the doctors wrote; "however, given the diagnosis [of] two autoimmune disorders requiring lifelong treatment, she has benefited from the emotional support from a counselor to cope with her new diagnoses and psychosocial stressors at home."

What makes the case unique: APS-2 is a relatively rare diagnosis, characterized by Addison's disease appearing alongside either type 1 diabetes, an autoimmune thyroid disease, or both.

The exact cause of the syndrome is not fully understood, but it has been tied to a number of gene variants, as well as environmental risk factors. Its presentation varies from patient to patient because different organs can be affected in each case. Patients often face delays in diagnosis due to this variation in disease presentation, the case reported authors noted.

"This case is unique because both diseases were diagnosed at the same time of presentation," they noted. "There are few cases that reported the concurrent diagnosis of T1DM [type 1 diabetes mellitus] and Addison's disease at initial presentation."

The case highlights the importance of screening patients with type 1 diabetes for additional autoimmune diseases, the doctors concluded. "Unexplained persistent electrolyte abnormalities" could raise a flag to screen for Addison's, they said, and that screening may include looking for adrenal antibodies, as they did in this case.

"Early detection could help prevent adrenal crisis, reducing morbidity and mortality associated with Addison's disease," they wrote.

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