Week 16 Q&A
A 15-year-old boy comes to the clinic because of concern about increased urination and thirst.
His teachers have noticed that he leaves class frequently at school, and he has also been getting up at night to urinate. He is obese but tells you he is pleased to have lost several pounds over the last several weeks. On exam, his height is at the 80th percentile, weight is at the 99th percentile, blood pressure is 130/80 mm Hg, and heart rate is 90 bpm. In general, he is obese but otherwise appears healthy. On exam, you note thickened and darkened skin on his posterior neck and axillae (see Figure 11–10), pink striae on his abdomen, and well-muscled legs and arms. You suspect that he could have type 2 diabetes mellitus but are smart enough to also consider type 1.
Acanthosis nigricans on the back of the neck. (Reproduced with permission from Hoffman BL, Schorge JO, Schaffer JI, et al, eds. Williams Gynecology. 2nd ed. New York, NY: McGraw-Hill Education; 2012, Fig. 17-6.)
Which of the following features would support a diagnosis of type 2 versus type 1 diabetes mellitus?
A. Recent weight loss.
B. Low C-peptide level.
C. Signs of insulin resistance (acanthosis nigricans).
D. Blood glucose of 280 mg/dL.
E. Polyuria and polydipsia.
The correct answer is “C.” The criteria for diagnosis of type 1 and type 2 diabetes are identical. (See Case 17, earlier.) In prepubertal children, all cases of new-onset diabetes should be considered type 1 unless there is overwhelming evidence to the contrary. In postpubertal children, factors that would support a diagnosis of type 2 diabetes include obesity, insidious onset, positive family history of type 2 diabetes, signs of insulin resistance (acanthosis nigricans, elevated insulin, elevated C-peptide), negative pancreatic antibodies, and high-risk race/ethnicity (ie, non-Hispanic black, Native American, Hispanic, Pacific Islander, and Asian American). If in doubt, it is safer to treat a patient as you would a confirmed case of type 1 diabetes, by administering insulin to prevent DKA.