Pathology of the GI Tract- SI and Colon (5) Flashcards
what is malabsorption characterized by?
defective absorption of fats, fat- and water- soluble vitamins, proteins, carbohydrates, electrolytes and minerals, and water
what is a hallmark of malabsorption?
steatorrhea
what is steatorrhea characterized by?
excessive fecal fat and bulky, frothy, greasy, yellow, or clay-colored stools
the chronic malabsorptive disorders most commonly encountered in the united states include what?
pancreatic insufficiency, celiac disease, and Crohn disease
Besides the common causes of malabsorptive disorders, what is another important cause of malabsorption that can be ruled out based on patient history?
intestinal graft-versus-host disease following allogenic hematopoietic stem cells transplantation
what is diarrhea defined as?
increase in stool mass, frequency, fluidity
isotonic stool and persists during fasting
secretory diarrhea
lactase deficiency, excessive osmotic forces exerted by unabsorbed luminal solutes
osmotic diarrhea
due to inflammatory disease is characterized by purulent bloody stools that continue during fasting?
exudative diarrhea
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?
whipple disease–> lymphatic transport
in cystic fibrosis, what does the loss of pancreatic exocrine secretion lead to?
it impairs fat absorption, and the associated avitaminosis A may contribute to squamous metaplasia of the pancreatic duct lining epithelium
what is meconium ileus?
in cystic fibrosis, thick viscid plugs of mucus may also be found in the small intestines of infants; sometimes these cause small bowel obstruction
autoimmunity seen in celiac disease arises from what?
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
what are two key features associated with celiac disease?
loss of the normal villus architecture and presence of an increased number of intraepithelial lymphocytes (IELs)
what is the diagnostic feature of celiac disease?
tTG antibody testing
how do children present with celiac disease?
m=f; 6-24 months: irritability, abdominal distention, chronic diarrhea, failure to thrive; extraintestinal: joint pain, anemia
what is dermatitis herpetiformis?
pruritic vesicular rash associated with celiac disease; IgA anti-gluten antibodies cross react with basement membrane proteins
almost all people with celiac disease carry what allele?
the class II HLA-DQ2 or HLA-DQ8 allele
where is environmental enteric dysfunction commonly seen?
in populations with poor sanitation and hygiene; parts of sub-saharan africa, such as Zambia; northern australia
what is the presentation of environmental enteric dysfunction?
malabsorption, malnutrition, and stunted growth
what is important to remember about environmental enteric dysfunction?
you don’t see anything under the microscope from a histologic standpoint–> no villus change
what is autoimmune enteropathy?
an x-linked disorder characterized by severe persistent diarrhea and autoimmune disease that occurs most often in young children
what is the severe familial form of autoimmune enteropathy?
IPEX
what causes familial form of autoimmune enteropathy (IPEX)?
germline loss of function mutations in the FOXP3 gene
what occurs in autoimmune enteropathy?
autoantibodies to enterocytes and goblet cells are common and some patients have antibodies to parietal cells or islet cells
how is autoimmune enteropathy different from celiac’s disease?
in contrast to celiac disease, neutrophils are often seen infiltrating the intestinal mucosa in cases of autoimmune enteropathy
what is the therapy for autoimmune enteropathy?
immunosuppressive drugs such as cyclosporine and hematopoietic stem cell transplantation
What are the effects of lactase deficiency?
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
what are the two forms of lactase deficiency?
congenital lactase deficiency and acquired lactase deficiency
what is the inheritance pattern of congenital lactase deficiency?
autosomal recessive
what population of people is acquired lactase deficiency common in?
native american, african american, and chinese populations
what is microvillus inclusion disease?
a rare autosomal recessive disorder of vesicular transport that leads to deficient brush-border assembly
what mutation causes microvillus inclusion disease?
mutation in MYO5B gene, which encodes for a motor protein
what is the effect of microvillus inclusion disease?
leads to the accumulation of abnormal apical vesicles containing microvilli and various membrane components
how can you detect microvillus inclusion disease?
abnormal vesicles can be identified by electron microscopy or by immunostaining for the brush border protein villin. CD10 immunohistochemistry used for diagnosis
where does microvillus inclusion disease occur most often?
in Europe, middle eastern, and Navajo Native american populations
what is the treatment for microvillus inclusion disease?
total parenteral nutrition and small bowel transplantation
what is abetalipoproteinemia?
a rare autosomal recessive disease characterized by an inability to assemble triglyceride-rich lipoproteins
what is the presentation of abetalipoproteinemia?
presents in infancy with failure to thrive, diarrhea, and steatorrhea; the plasma is completely devoid of lipoproteins containing apolipoprotein B
what does abetalipoproteinemia result in?
failure to absorb essential fatty acids leads to deficiencies of fat-soluble vitamins as well as lipid membrane defects
how can the lipid membrane defects that are present in abetalipoproteinemia recognized?
by the presence of acanthocytes in peripheral blood smears
what mutation causes abetalipoprotenemia?
mutation in MTP gene
what is the MTP gene required for?
transfer of lipids to nascent apolipoprotein B polypeptide in the endoplasmic reticulum
what happens if there is no MTP gene?
lipids accumulate intracellularly
