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Gastrointestinal 2 > Pathology of Malabsorption > Flashcards

Pathology of Malabsorption Flashcards

1
Q

What is malabsorption?

A

defective absorption of fats, vitamins, proteins, carbohydrates, electrolytes, minerals and water.

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2
Q

What will you see with malabsorption?

A
  • chronic diarrhea
  • weight loss, fatigue, anemia
  • steatorrhea (excessive fecal fat)
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3
Q

What are some mechanisms by which malabsorption can occur?

A
  1. intraluminal digestion disturbance= luminal substances are broken down for absorption.
  2. terminal digestion disturbance= hydrolysis of carbohydrates and proteins in the small intestine mucosa.
  3. transepithelial transport disturbance= nutrients, fluid, and electrolytes are transported across and enter the small intestine epithelium.
  4. lymphatic transport disturbance= absorbed lipids can not be transported.
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4
Q

What is CELIAC disease?

A

immune mediated enteropathy associated with ingestion of gluten in genetically susceptible people.

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5
Q

What is GLUTEN?

A

a protein in barley, rye, and wheat. The alcohol-soluble fraction of gluten, GLIADIN is what causes the pathology.

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6
Q

What does GLIADIN do?

A
  • some gliadin peptides induce proliferation of CD8 intraepithelial lymphocytes, inducing NK cells to injur enterocytes.
  • gliadin can also induce T cells to cause the characteristic mucosal pathology.
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7
Q

*** What major genes have been associated with Celiac disease?

A

HLA-DQ2 and DQ8 genotypes.

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8
Q

*** What serum antibodies have been associated with Celiac disease?

A

IgA class ANTITISSUE TRANSGLUTAMINASE (AntitTG), ANTIENDOMYSIAL ANTIBODY (EMA) AND ANTIGLIADIN ANTIBODIES (AGA).

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9
Q

What happens to the villi in celiacs?

A

they are lost, decreasing surface area for absorption

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10
Q

What are the associated conditions with celiacs?

A
  • family history of celiac disease
  • autoimmune diseases
  • T1DM
  • Thyroiditis
  • IgA deficiency
  • genetic syndromes (down syndrome, turners…)
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11
Q

What are the clinical features of celiac disease?

A
  • anemia
  • osteoporosis
  • neurological problems (from not absorbing enough vit B6).
  • chronic diarrhea
  • weight loss
  • DERMATITIS HERPETIFORMIS (an itchy, blistering skin disease that resembles herpes).
  • lymphocytic gastritis
  • lymphocytic colitis
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12
Q

Can celiac disease present in infancy?

A

YES, presenting as failure to thrive, diarrhea, abdominal distention, and developmental delay. These symptoms present upon weaning of child from mothers breast milk to normal diet.

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13
Q

How may older children present with celiac disease?

A

short stature or dental enamel defects.

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14
Q

How may adults present with celiac disease?

A

diarrhea, constipation, flatus, belching, anemia, weight loss, or vitamin deficiencies.

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15
Q

What are some atypical symptoms of celiac disease?

A
  • few or no GI symptoms
  • iron deficiency
  • osteoporosis
  • infertility
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16
Q

What are the 3 histological categories of celiac disease?

A
  • Marsh I= marked infiltration of villous epithelium by lymphocytes.
  • Marsh II= intraepithelial lymphocytosis and elongation and branching of crypts with increased epithelial cells.
  • Marsh III= intraepithelial lymphocytosis, crypthyperplasia and villous atrophy.
17
Q

What is tropical sprue?

A
  • unrelated to gluten sensitivity, but malabsorption (due to partial villous atrophy with lymphocytes) becomes apparent within a few days or weeks of an acute enteric diarrheal infection.
  • usually seen in tropics.
  • may be related to enterotoxigenic E. coli
18
Q

To what does tropical sprue respond?

A

folic acid, vitamin B12, and tetracycline

19
Q

What is autoimmune enteropathy?

A
  • x linked autoimmune disorder causing persistent diarrhea in young children.
  • IPEX= Immune dysregulation, Polyendocrinopathy, Enteropathy, and X linkage due to a germ-line mutation in the FOXP3 gene on the X chromosome.
20
Q

What happens in autoimmune enteropathy?

A
  • defective T cell regulation

- autoantibodies against enterocytes and goblet cells

21
Q

What is lactase (disaccharidase) deficiency?

A
  • lactase is the enzyme found on the brush border of villi. A deficiency in this enzyme results in a villous absorptive defect.
22
Q

If you biopsied a villous in a person with lactase deficiency would it look normal?

A

YES (aka histology is unremarkable)

23
Q

What are the 2 types of lactase deficiency?

A
  1. congenital= mutation in the gene coding for lactase. Exposure to milk products causes explosive diarrhea.
  2. Acquired= due to a down regulation of lactase gene expression. Disease presents after childhood and causes abdominal fullness, diarrhea and flatulence.
24
Q

What is abetalipoproteinemia?

A
  • rare autosomal recessive disease causing an inability to secrete triglyceride rich lipoproteins.
  • caused by a mutation in the microsomal triglyceride transfer protein (MTP), which catalyzes transport of triglycerides, cholesterol esters, and phospholipids.
25
Q

In what does MTP deficient enterocytes result, in abetalipoproteinemia?

A
  • the enterocytes can not transport lipoproteins and free fatty acids.
  • monoglycerides can not be assembled into chylomicrons and triglycerides accumulate in epithelial cells.
26
Q

What is seen microscopically after fatty meals in the small intestinal epithelial cells in abetalipoproteinemia?

A

lipid vacuolization

27
Q

How and when does abetalipoproteinemia present?

A
  • in infancy with failure to thrive and steatorrhea.
  • lipid membrane defects lead to acantholytic RBCs (loss of intracellular connections).
  • also deficiency in fat soluble vitamins.
28
Q

What is Whipples disease?

A
  • small intestinal mucosa is laden with macrophages that contain rod shaped bacilli (tropheryma whippelii). Similar macrophages can been seen in the CNS, lymph nodes, and spleen.
29
Q

*** What is the demographic for whipples disease?

A

white middle aged males

30
Q

*** What are the clinical symptoms of whipples disease?

A

malabsorption with CNS symptoms, polyarthrits, and hyperpigmentation

31
Q

In general what are the consequences of long standing malabsorption?

A
  • hematopoietic= anemia and bleeding disorders (loss of vitamin K).
  • musculoskeletal= osteopenia and tetany.
  • endocrine= amenorrhea and infertility.
  • skin= purpura, petechiae, dermatitis.
  • nervous system= peripheral neuropathy (loss of vitamin B).

Gastrointestinal 2 (18 decks)

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