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Chapter 223: Type 1 Diabetes Mellitus

Nikhil Goyal; Adam B. Schlichting

INTRODUCTION AND EPIDEMIOLOGY

During 2002–2005, 15,600 people under 20 years of age were newly diagnosed with type 1 diabetes annually in the United States.1 Classification of diabetes (American Diabetes Association) is shown in Table 223-1.2,3

TABLE 223-1Etiologic Classification of Diabetes Mellitus
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TABLE 223-1 Etiologic Classification of Diabetes Mellitus

  • Type 1 diabetes (β-cell destruction, usually leading to absolute insulin deficiency)

    1. Immune mediated

    2. Idiopathic

  • Type 2 diabetes (may range from predominantly insulin resistance with relative insulin deficiency to a predominantly secretory defect with insulin resistance)

  • Other specific types, such as

    1. Genetic defects of β-cell function

    2. Genetic defects in insulin action

    3. Diseases of the exocrine pancreas (pancreatitis, trauma, cystic fibrosis, etc.)

    4. Endocrinopathies (Cushing's syndrome, pheochromocytoma, hyperthyroidism, somatostatinoma, glucagonoma, etc.)

    5. Drug- or chemical-induced (interferon-α, β-adrenergic agonists, diazoxide, phenytoin [Dilantin®], glucocorticoids, nicotinic acid, pentamidine, thiazides, thyroid hormone, pyrinuron [Vacor®], etc.)

    6. Infections (congenital rubella, cytomegalovirus, etc.)

    7. Uncommon forms of immune-mediated diabetes

    8. Other genetic syndromes sometimes associated with diabetes (Down's syndrome, Klinefelter's syndrome, Turner's syndrome, etc.)

  • Gestational diabetes mellitus

PATHOPHYSIOLOGY

Type 1 diabetes is characterized by almost no circulating insulin and the failure of β-cells to respond to insulinogenic stimuli. This accounts for only 5% to 10% of all cases of diabetes and is mostly diagnosed in children and young adults, with peaks before school age and at puberty. Immune-mediated destruction of β-cells causes 90% of these cases, and the remainder have no known cause. Spontaneous ketoacidosis almost always develops in untreated cases, and insulin is required for survival. It is often not possible to clearly classify patients as type 1 or type 2 in the ED.3

Chapter 224, Type 2 Diabetes Mellitus, discusses type 2 diabetes mellitus in detail. Hyperglycemia is present in all types of diabetes mellitus and is the main factor responsible for complications. Therefore, maintaining euglycemic control is the cornerstone of management.

DIAGNOSIS

The American Diabetes Association criteria for diagnosis are listed in Table 223-2.2,3 Any one of these can be used to make the diagnosis. Patients with a fasting plasma glucose of 100 milligrams/dL to 125 milligrams/dL (5.6-7.0 mmol/L), a hemoglobin A1C of 5.7% to 6.4%, or a 2-hour plasma glucose of 140 to 199 milligrams/dL (7.8-11.0 mmol/L) as part of an oral glucose tolerance test are classified as having prediabetes.2

TABLE 223-2American Diabetes Association Criteria for the Diagnosis of Diabetes
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TABLE 223-2 American Diabetes Association Criteria for the Diagnosis of Diabetes
A1C ≥6.5%* The test should be performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay.

Or

Fasting plasma glucose ≥126 milligrams/dL (7.0 mmol/L)*

 Fasting is defined as no caloric intake ...

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