DISCUSSION: SECONDARY DIABETES
It is well known that the prevalence of diabetes is skyrocketing, and medical offices are filled with affected patients. According to a 2011 report from the CDC, 90% to 95% of all diabetes cases are type 2, 5% are type 1 (autoimmune), and the rest (about 1% to 5%) are “other types” of diabetes.3 Due to these disproportionate statistics, clinicians often overlook the possibility of uncommon etiologies and assume all patients with diabetes have type 2—especially when the patient is overweight or obese.
Table 2 lists conditions and medications that may contribute to significant hyperglycemia.4 Some contributors are rather obvious (eg, status post pancreatectomy) or have no impact on treatment strategy (eg, chromosomal defects such as Down or Turner syndrome). However, certain conditions, such as Cushing syndrome, acromegaly, and hemochromatosis, can be relatively hard to recognize due to the variable rate of clinical manifestation, especially in the earlier stages of the disease. Experts have raised concerns that the prevalence of secondary diabetes (1% to 5%) may actually be underestimated due to “misdiagnosis” as T2DM.
Early detection of the underlying disorder, followed by initiation of appropriate treatment, is critical. It will not only improve but also may resolve the patient’s hyperglycemia, and it may also reverse or stop the damage to other vital organs.
The case patient had an unfortunate situation in which her Cushing syndrome was masked by commonly encountered diagnoses of hypertension, T2DM, obesity, and depression. Cushing is an easy diagnosis to miss, since it has an insidious onset and it can take more than five years for some of the physical findings to become evident.
Pancreatic cancer is another uncommon but critical disease worth mentioning. Pancreatic cancer should be in the differential diagnosis for previously euglycemic patients who experience abrupt elevation of glucose or previously well-managed patients whose glucose values quickly get out of control without obvious cause (eg, medication cessation, addition of glucocorticoid therapy, uncontrolled diet).
In our practice, we have encountered three patients with pancreatic cancer in this setting. The only sign was a sudden rise in glucose (300 to 500 mg/dL throughout the day) in patients whose A1C had been low (in the 6% range) with one or two oral medications. Thorough history taking did not reveal any potential causes for sudden hyperglycemia. Only one patient had a palpable mass on abdominal exam and elevated liver enzymes and bilirubin. Unfortunately, that patient died eight months later. The other two had favorable outcomes from surgery and chemotherapy. Early detection was the key for those two patients.
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