Pathology of the GI Tract- SI and Colon (5)

Question 1

what is malabsorption characterized by?

Answer 1

defective absorption of fats, fat- and water- soluble vitamins, proteins, carbohydrates, electrolytes and minerals, and water

Question 2

what is a hallmark of malabsorption?

Answer 2

steatorrhea

Question 3

what is steatorrhea characterized by?

Answer 3

excessive fecal fat and bulky, frothy, greasy, yellow, or clay-colored stools

Question 4

the chronic malabsorptive disorders most commonly encountered in the united states include what?

Answer 4

pancreatic insufficiency, celiac disease, and Crohn disease

Question 5

Besides the common causes of malabsorptive disorders, what is another important cause of malabsorption that can be ruled out based on patient history?

Answer 5

intestinal graft-versus-host disease following allogenic hematopoietic stem cells transplantation

Question 6

what is diarrhea defined as?

Answer 6

increase in stool mass, frequency, fluidity

Question 7

isotonic stool and persists during fasting

Answer 7

secretory diarrhea

Question 8

lactase deficiency, excessive osmotic forces exerted by unabsorbed luminal solutes

Answer 8

osmotic diarrhea

Question 9

due to inflammatory disease is characterized by purulent bloody stools that continue during fasting?

Answer 9

exudative diarrhea

Question 10

in many malabsorptive disorders, a defect in one of these processes predominates, but several usually contribute; however what diarrheal disease only has one defect in malabsorption and what is it?

Answer 10

whipple disease–> lymphatic transport

Question 11

in cystic fibrosis, what does the loss of pancreatic exocrine secretion lead to?

Answer 11

it impairs fat absorption, and the associated avitaminosis A may contribute to squamous metaplasia of the pancreatic duct lining epithelium

Question 12

what is meconium ileus?

Answer 12

in cystic fibrosis, thick viscid plugs of mucus may also be found in the small intestines of infants; sometimes these cause small bowel obstruction

Question 13

autoimmunity seen in celiac disease arises from what?

Answer 13

from a combination of the inheritance of susceptibility genes, which may contribute to the breakdown of self-tolerance, and environmental triggers, such as infections and tissue damage, which promote the activation of self-reactive lymphocytes

Question 14

what are two key features associated with celiac disease?

Answer 14

loss of the normal villus architecture and presence of an increased number of intraepithelial lymphocytes (IELs)

Question 15

what is the diagnostic feature of celiac disease?

Answer 15

tTG antibody testing

Question 16

how do children present with celiac disease?

Answer 16

m=f; 6-24 months: irritability, abdominal distention, chronic diarrhea, failure to thrive; extraintestinal: joint pain, anemia

Question 17

what is dermatitis herpetiformis?

Answer 17

pruritic vesicular rash associated with celiac disease; IgA anti-gluten antibodies cross react with basement membrane proteins

Question 18

almost all people with celiac disease carry what allele?

Answer 18

the class II HLA-DQ2 or HLA-DQ8 allele

Question 19

where is environmental enteric dysfunction commonly seen?

Answer 19

in populations with poor sanitation and hygiene; parts of sub-saharan africa, such as Zambia; northern australia

Question 20

what is the presentation of environmental enteric dysfunction?

Answer 20

malabsorption, malnutrition, and stunted growth

Question 21

what is important to remember about environmental enteric dysfunction?

Answer 21

you don’t see anything under the microscope from a histologic standpoint–> no villus change

Question 22

what is autoimmune enteropathy?

Answer 22

an x-linked disorder characterized by severe persistent diarrhea and autoimmune disease that occurs most often in young children

Question 23

what is the severe familial form of autoimmune enteropathy?

Answer 23

IPEX

Question 24

what causes familial form of autoimmune enteropathy (IPEX)?

Answer 24

germline loss of function mutations in the FOXP3 gene

Question 25

what occurs in autoimmune enteropathy?

Answer 25

autoantibodies to enterocytes and goblet cells are common and some patients have antibodies to parietal cells or islet cells

Question 26

how is autoimmune enteropathy different from celiac’s disease?

Answer 26

in contrast to celiac disease, neutrophils are often seen infiltrating the intestinal mucosa in cases of autoimmune enteropathy

Question 27

what is the therapy for autoimmune enteropathy?

Answer 27

immunosuppressive drugs such as cyclosporine and hematopoietic stem cell transplantation

Question 28

What are the effects of lactase deficiency?

Answer 28

dietary lactose cannot be broken into glucose and galactose; lactose cannot be absorbed and remains in the lumen where it exerts an osmotic force that attracts fluid and causes diarrhea

Question 29

what are the two forms of lactase deficiency?

Answer 29

congenital lactase deficiency and acquired lactase deficiency

Question 30

what is the inheritance pattern of congenital lactase deficiency?

Answer 30

autosomal recessive

Question 31

what population of people is acquired lactase deficiency common in?

Answer 31

native american, african american, and chinese populations

Question 32

what is microvillus inclusion disease?

Answer 32

a rare autosomal recessive disorder of vesicular transport that leads to deficient brush-border assembly

Question 33

what mutation causes microvillus inclusion disease?

Answer 33

mutation in MYO5B gene, which encodes for a motor protein

Question 34

what is the effect of microvillus inclusion disease?

Answer 34

leads to the accumulation of abnormal apical vesicles containing microvilli and various membrane components

Question 35

how can you detect microvillus inclusion disease?

Answer 35

abnormal vesicles can be identified by electron microscopy or by immunostaining for the brush border protein villin. CD10 immunohistochemistry used for diagnosis

Question 36

where does microvillus inclusion disease occur most often?

Answer 36

in Europe, middle eastern, and Navajo Native american populations

Question 37

what is the treatment for microvillus inclusion disease?

Answer 37

total parenteral nutrition and small bowel transplantation

Question 38

what is abetalipoproteinemia?

Answer 38

a rare autosomal recessive disease characterized by an inability to assemble triglyceride-rich lipoproteins

Question 39

what is the presentation of abetalipoproteinemia?

Answer 39

presents in infancy with failure to thrive, diarrhea, and steatorrhea; the plasma is completely devoid of lipoproteins containing apolipoprotein B

Question 40

what does abetalipoproteinemia result in?

Answer 40

failure to absorb essential fatty acids leads to deficiencies of fat-soluble vitamins as well as lipid membrane defects

Question 41

how can the lipid membrane defects that are present in abetalipoproteinemia recognized?

Answer 41

by the presence of acanthocytes in peripheral blood smears

Question 42

what mutation causes abetalipoprotenemia?

Answer 42

mutation in MTP gene

Question 43

what is the MTP gene required for?

Answer 43

transfer of lipids to nascent apolipoprotein B polypeptide in the endoplasmic reticulum

Question 44

what happens if there is no MTP gene?

Answer 44

lipids accumulate intracellularly