Pancreas

Diabetes mellitus

Diabetes mellitus



Last author update: 1 August 2012
Last staff update: 19 January 2023

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PubMed Search: Diabetes mellitus pancreas

Deepali Jain, M.D.
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Cite this page: Jain D. Diabetes mellitus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/pancreasdmgeneral.html. Accessed February 6th, 2023.
Definition / general
Epidemiology
Etiology
  • Destruction of islets due to drugs (steroids, thiazides, pentamidine), hemochromatosis ("bronze diabetes" due to hemosiderin deposition in pancreas), hereditary ceruloplasmin deficiency (Hum Pathol 1997;28:499), infections (congenital rubella, CMV, coxsackievirus [Arch Pathol Lab Med 1980;104:438], enteroviruses [Diabetologia 2004;47:225]), pancreatitis, surgery, tumors, endocrinopathies (pituitary, adrenal, pregnancy) or idiopathic
Type 1

Etiology
  • Presumed autoimmune cause for islet cell destruction but precise etiology unclear (Wikipedia: Diabetes Mellitus Type 1 [Accessed 8 December 2017])
  • Usually Northern European descent
  • 70% concordance in identical twins, HLA-D linked
  • Genetic predisposition may affect immune responsiveness to a beta cell autoantigen or method of presentation to T cells

Viruses and IDDM:
  • Viruses may damage beta cells, exposing antigens which trigger an autoimmune response
  • May be due to molecular mimicry (immune response develops against shared amino acid sequences): GAD and Coxsackie B4 virus share a six amino acid sequence
  • Retrovirus may serve as a superantigen

Autoimmune aspects:
  • Islet cell autoantibodies present in 70%; also CD8+ T cell infiltrate in islets
  • Antigens are glutamic acid decarboxylase (GAD), islet autoantigen 2, insulin associated antibody, gangliosides
  • GAD antibodies precede clinical symptoms, present in most newly diagnosed patients and 80% of first degree relatives
  • GAD antibody also causes stiff man syndrome, whose patients often have a history of IDDM
  • Many IDDM patients also have antithyroid peroxidase, antiparietal cell and antiadrenocortical antibodies
  • Some NIDDM patients have autoantibodies but no other features of IDDM
  • Usually chronic (years)
  • Clinical disease when 90% of islet cells are destroyed

Clinical features
  • Onset at age < 20 years, normal weight (unlike most NIDDM)
  • Characterized by PPP (polyuria, polydipsia, polyphagia) and ketoacidosis (DKA)
  • Polyphagia combined with weight loss is specific for IDDM; type 2 patients rarely have either
  • Severe fasting hypoglycemia is due to cessation of glycogen storage in fat and muscle
  • Glycosemia causes glycosuria with depletion of water and electrolytes
  • Also: low / absent plasma insulin, high plasma glucagon, unstable glucose tolerance (very sensitive to changes in insulin, diet, exercise, infection, stress), presence of free fatty acids (due to breakdown of adipose stores), which produces ketone bodies (acetoacetic acid and beta hydroxybutyric acid)
  • May get hyperosmotic nonketotic coma - dehydration due to hyperglycemic diuresis with failure to drink enough fluids to compensate, often in an elderly person with diabetes and stroke / infection
  • "Dead in bed syndrome": sudden death in young people with type 1 diabetes, cause unknown (Hum Pathol 2010;41:392)
Type 2 (NIDDM)
  • Also called adult onset, non insulin dependent diabetes mellitus / NIDDM, type 2
  • 80 - 90% of cases of diabetes (Wikipedia: Diabetes Mellitus Type 2 [Accessed 8 December 2017])
  • Usually > 30 years old, obese (80% of cases, abdominal obesity more important than subcutaneous obesity), normal or increased blood insulin, rare diabetic ketoacidosis, no anti-islet antibodies

Pathophysiology
Early:
  • Normal insulin secretion and plasma levels but loss of pulsatile, oscillating pattern of secretion
  • Also loss of rapid first phase of insulin secretion triggered by glucose
  • NO insulinitis is present

Later:
  • Mild / moderate insulin deficiency, may be due to beta cell damage
  • Beta cells may be "exhausted" due to chronic hyperglycemia and persistent beta cell stimulation

Amylin:
  • 37 amino acid peptide, normally produced by beta cells, packaged and cosecreted with insulin
  • In NIDDM patients, tends to accumulate outside beta cells and resembles amyloid

Clinical features
  • 90%+ concordance in twins, apparently due to multiple genetic polymorphisms (no HLA association)
  • Due to insulin resistance (associated with obesity and pregnancy) or derangement in beta cell secretion of insulin
  • Associated with amyloid deposits in islets (amyloid associated with basement membrane heparan sulfate proteoglycan) (Arch Pathol Lab Med 1992;116:951) and pituitary (Arch Pathol Lab Med 1995;119:1055)
Maturity onset diabetes of the young
Diagrams / tables

Images hosted on other servers:

Single gene mutations
resulting in monogenic
diabetes / MODY

Clinical complications
General
  • Main complications are microangiopathy, retinopathy, nephropathy, neuropathy - all due to hyperglycemia
  • Kidneys transplanted into diabetic patients develop nephropathy within 3 - 5 years but kidneys from diabetic patients transplanted into normal patients have remission of nephropathy
  • Strict control of diabetes delays progression of microvascular complications
  • Complications are due to nonenzymatic glycosylation and disturbances in polyol pathways

Nonenzymatic glycosylation
  • Glucose + protein => Schiff base (protein - NH = CH (CHOH)4-CH2OH) => Amadori product
  • (protein - NH-CH2-C = 0-(CHOH)3-CH2OH) => protein - protein cross linking via N-C-N bonding
  • Early reactions are reversible and related to HbA1c level
  • Advanced glycosylation end products (AGE) are not reversible
  • AGE traps LDL in blood vessels, enhances cholesterol deposition, accelerating atherosclerosis
  • AGE inhibition antagonizes diabetic complications in experimental models

Vascular complications
  • Relative risk is 100:1
  • Accelerated atherosclerosis in aorta and large / medium sized vessels
  • Myocardial infarction: most common cause of death, no gender preference
  • Gangrene of lower extremities
  • Micro description:
    • Hyaline arteriolosclerosis, associated with hypertension, more common / severe in diabetes but not specific
    • Amorphous hyaline thickening in arteriolar wall
    • Related to severity of disease and hypertension
    • Microangiopathy: diffuse basement membrane thickening with protein leakage in capillaries of skin, skeletal muscle, retina, renal glomeruli, renal medulla, renal tubules, Bowman capsule, peripheral nerves, placenta

Diabetic renal disease
Ocular
  • #4 cause of blindness in U.S.
  • Associated with retinopathy, cataracts, glaucoma
  • Polyol pathways: important in lens and other tissues (nerves, kidney, blood vessels) that don't require insulin for glucose transport
    • High intracellular glucose plus aldose reductase produces sorbitol and later fructose, causing water influx and osmotic cell injury
    • In lens, causes swelling and opacity
    • Inhibition of sorbitol may reduce formation of cataracts and neuropathy

Neuropathy
  • Peripheral, symmetric neuropathy of lower extremity most common, sensory more common than motor
Diagnosis
  • High fasting glucose or impaired glucose tolerance (without diabetes, oral glucose loads cause only slight rise in blood glucose due to brisk insulin response; with diabetes, blood glucose rises markedly for a sustained period)
Case reports
Treatment
Microscopic (histologic) description
  • Type 1: inconsistent reduction in number and size of islets, uneven insulinitis (T lymphocytes)
  • Type 1: early insulinitis with marked islet atrophy and fibrosis and severe beta cell depletion (Islets 2011;3:131)
  • Type 2: subtle reduction in islet cell mass, amyloid replacement of islets due to amylin fibrils (also seen in aging nondiabetics); associated with marked fatty replacement
  • Type 2: amyloid in the islets of Langerhans is the uniform pathologic feature
  • Gestational diabetes: lower total insulin+ area due to smaller islets (Islets 2011;3:231)
  • Infants of diabetic mothers: islet cell hypertrophy / hyperplasia
Videos

Histopathology pancreas: type 2 diabetes mellitus

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