MKSAP Quiz: Hyperglycemia in a middle-aged man
This month's quiz asks readers to evaluate a 51-year-old man for a 9-month history of chronic abdominal pain.
A 51-year-old man is evaluated for a 9-month history of chronic abdominal pain. He has a long-standing history of alcoholism and has been admitted to the hospital several times in the past 8 years for gastrointestinal bleeding and acute pancreatitis. A review of symptoms is positive only for a 5.5-kg (12.1-lb) weight loss over the past year. He currently takes no medications.
Vital signs are normal, and BMI is 23. Physical examination reveals a scaphoid-appearing abdomen with normal bowel sounds and diffuse abdominal tenderness to palpation without guarding.
His fasting plasma glucose level is 175 mg/dL (9.7 mmol/L), and a repeat fasting plasma glucose level is 182 mg/dL (10.1 mmol/L).
A CT scan of the abdomen reveals diffuse pancreatic calcifications.
Which of the following is the best categorization of this patient's diabetes mellitus?
A. Late-onset autoimmune diabetes of adulthood
B. Secondary diabetes
C. Type 1 diabetes
D. Type 2 diabetes
MKSAP Answer and Critique
The correct answer is B) Secondary diabetes. This item is available to MKSAP 15 subscribers as item 17 in the Endocrinology section. Part A of MKSAP 16 will be released on July 31. More information is available online.
Diabetes mellitus is generally categorized as type 1, type 2, gestational, and secondary diabetes. This patient's diabetes is the last type, which consists of a group of unrelated conditions that are associated with hyperglycemia through effects on either insulin availability or insulin sensitivity. These include various endocrine disorders, such as Cushing syndrome and acromegaly; several pancreatic conditions, such as acute and chronic pancreatitis and pancreatic cancer; drug-induced hyperglycemia; and several genetic syndromes. This patient has a history of ethanol abuse and chronic abdominal pain, which may be related to chronic pancreatitis. The most common cause of chronic pancreatitis in western industrialized countries is chronic alcohol abuse, which accounts for 50% or more of all cases. The presence of pancreatic calcifications on radiographs confirms the diagnosis. Although plain films of the abdomen will show pancreatic calcifications in some patients, most patients will require abdominal CT scans to exclude other causes of pain.
Patients with pancreatic disease causing secondary diabetes may still respond to oral sulfonylureas, and a trial of such a drug is appropriate. If there has been enough loss of beta cell mass, however, insulin therapy may be required. Because of glucagon deficiency, patients with diabetes related to pancreatic insufficiency may be predisposed to hypoglycemia.
Late-onset autoimmune diabetes of adulthood is a possibility in this patient, given his age (51 years), his lean body habitus, and the insidious onset of diabetes. However, it would be much less common than secondary diabetes in this man with confirmed chronic pancreatitis.
This patient's clinical presentation is atypical for type 1 diabetes, which usually has an acute or subacute onset and is characterized by polyuria, polydipsia, polyphagia, and weight loss.
Most patients with type 2 diabetes are obese or at least have abdominal obesity (high waist-to-hip ratio). This patient is of normal body weight, and his scaphoid-appearing abdomen makes type 2 diabetes even less likely.
Key Point
- Secondary causes of diabetes mellitus should be considered in any patient who presents with atypical features.