robbins cns GI malabsorption misc

Question 1

Diarrhea is defined as

Answer 1

1. an increase in stool mass, frequency, or fluidity, typically greater than 200 gm per day.
2. In severe cases stool volume can exceed 14 L per day and, without fluid resuscitation, result in death.

Question 2

Painful, bloody, small-volume diarrhea is known as

Answer 2

dysentery

Question 3

characterized by isotonic stool and persists during fasting.

Answer 3

Secretory diarrhea is characterized by isotonic stool and persists during fasting.

Question 4

due to the excessive osmotic forces exerted by unabsorbed luminal solutes. Diarrhea fluid is more than 50 mOsm more concentrated than plasma and abates with fasting.

Answer 4

Osmotic diarrhea , such as that which occurs with lactase deficiency, is due to the excessive osmotic forces exerted by unabsorbed luminal solutes. The diarrhea fluid is more than 50 mOsm more concentrated than plasma and abates with fasting.

Question 5

follows generalized failure of nutrient absorption, is associated with steatorrhea, and is relieved by fasting.

Answer 5

Malabsorptive diarrhea follows generalized failure of nutrient absorption, is associated with steatorrhea, and is relieved by fasting.

Question 6

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

Answer 6

Exudative diarrhea due to inflammatory disease is characterized by purulent, bloody stools that continue during fasting.

Question 7

what digestive disease will occur in more than 80% of patients with cystic fibrosis?

Answer 7

pancreatic insufficiency via chronic autodigestion of pancrease

Reduced hydration can occasionally lead to intestinal obstruction, but commonly results in formation of pancreatic intraductal concretions.

The latter can begin in utero, and result in duct obstruction, low-grade chronic autodigestion of the pancreas, and eventual exocrine pancreatic insufficiency in more than 80% of patients.

The result is failure of the intraluminal phase of nutrient absorption, which can be effectively treated in most patients with oral enzyme supplementation.

Question 8

_____contains most of the disease-producing components in celiac disease

_____ is 33-amino acid peptide which resists degradation by gastric, pancreatic, and small intestinal proteases

Answer 8

gliadin, which is the the alcohol-soluble fraction of gluten

α-gliadin

Question 9

1) What is the theorized cascade of events leading to gluten sensitive enteropathy: initiation mechanism of epithelial breakdown

Answer 9

gliadin peptides induce epithelial cells to express IL-15—> triggers activation/proliferation of intraepithelial CD8 lymphocytes which express NKG2D (natural kill cell marker)—> recognizes MICA-A expressing enterocytes, in turn attacked by NKG2D-expressing intraepithelial lymphocytes.–> epithelial break down

Question 10

2) What is the theorized cascade of events leading to gluten sensitive enteropathy: what form of gliadin peptide activates an immune response after entering into the lamina propria?

Answer 10

1. deaminated
2. alpha gliadian peptides diffuse into the lamina propria –> gliadin is deamidated by tissue transglutaminase–> deaminated gliadin peptides (DGP)
3. DGP interacts with HLA-DQ2 or HLA-DQ8 APCs –> stimulate CD4+ T cells to produce cytokines that contribute to tissue damage.
4. Both inate (CD8) and adaptive (CD4) immune responses

Question 11

almost all people with celiac disease carry the class II HLA-DQ2 or HLA-DQ8 allele. However _______ accounts for less than half of the genetic component of celiac disease.

Answer 11

1. the class II HLA-DQ2 or HLA-DQ8 allele.
2. However, the HLA locus accounts for less than half of the genetic component of celiac disease.

Question 12

associations between celiac disease and other diseases

Answer 12

Autoimmune disease

1. including type 1 diabetes
2. thyroiditis
3. Sjögren syndrome
4. IgA nephropathy

neurologic disorders with

1. ataxia
2. autism
3. depression
4. epilepsy
5. Down syndrome
6. Turner syndrome

Question 13

resolution of symptoms in CD

Answer 13

decreasing titers of anti-tissue transglutaminase +r other celiac disease-associated antibodies (??) –> restoration of normal or near normal mucosal histology within 6 to 24 months.

Question 14

Celiac dx:

1. M:F
2. Associated symptoms..
3. May present with…

Answer 14

1. In adults: women 2x: men. monthly menstrual bleeding may accentuate effects of impaired absorption.
2. associated with
   
   1. chronic diarrhea
   2. bloating
   3. chronic fatigue
   4. often asymptomatic.
3. may present with anemia due to chronic iron and vitamin malabsorption

Question 15

Celical Dx Pediatric cases

1. M:F
2. extaintestinal complaints
3. symptoms
4. Classic symptoms & nonclassic symptoms

Answer 15

1. males and females equally
2. Common extraintestinal complaints
   
   1. arthritis or joint pain
   2. aphthous stomatitis
   3. iron deficiency anemia
   4. delayed puberty
   5. short stature.
3. classic symptoms
   
   1. typically begins after intrduction of gluten to the diet between ages of 6 and 24 months
   2. manifests as irritability, abdominal distention, anorexia, chronic diarrhea, failure to thrive, weight loss, or muscle wasting.
4. nonclassic symptoms
   
   1. tend to present at older ages with complaints of abdominal pain, nausea, vomiting, bloating, or constipation.
      2.

Question 16

Answer 16

dermatitis herpetiformis

A characteristic itchy, blistering skin lesion may be present in as many as 10% of patients with celiac disease

Question 17

Answer 17

A characteristic itchy, blistering skin lesion, dermatitis herpetiformis ( Chapter 25 ), can be present in as many as 10% of patients with celiac disease

Question 18

Testing for Celiac Disease

1. what is the preferred order of tests?
2. What is the most sensitive serological test for CD?
3. what are other tests?
4. What is NOT useful for confirming diagnosis but can be useful to exclude?

Answer 18

1. Noninvasive serologic tests performed prior to biopsy.
2. Most sensitive tests: measurement of IgA Abs against tissue transglutaminase.
3. IgA anti-endomysial Abs can also be present.
4. IgG anti-tissue transglutaminase antibodies may be detected in patients with IgA deficiency.
5. The absence of HLA-DQ2 and HLA-DQ8 is useful for its high negative predictive value, but the presence of these alleles is not helpful in confirming the diagnosis.

Question 19

Individuals with celiac disease have a higher than normal rate of _____, which consists of

Answer 19

malignancy

most common celiac disease-associated cancer is enteropathy-associated T-cell lymphoma, an aggressive lymphoma of intraepithelial T lymphocytes

Question 20

1. tropical sprue
2. where it occurs
3. what it causes
4. diagnostic criteria
5. global impact

Answer 20

1. Environmental enteropathy
2. prevalent in areas and populations with poor sanitation and hygiene
3. individuals often suffer from malabsorption and malnutrition, stunted growth, and defective intestinal mucosal immune function
4. no accepted clinical, laboratory, or histopathologic criteria that allow diagnosis of environmental enteropathy
5. global impact of environmental enteropathy, which is estimated to affect more than 150 million children worldwide and may contribute to a very large number of childhood deaths, is difficult to overstate.

Question 21

Autoimmune enteropathy

Answer 21

1. an X-linked disorder
2. characterized by severe persistent diarrhea and autoimmune disease that occurs most often in young children.
3. IPEX: severe familial form termed “immune dysregulation, polyendocrinopathy, enteropathy, and X-linkage”
   
   1. it is a germline mutation in the FOXP3 gene located on the X chromosome.
   2. FOXP3: transcription factor expressed in CD4+ regulatory T cells
4. Autoantibodies to
   
   1. enterocytes and goblet cells common
   2. parietal or islet cells in some instances
5. Within small intestine: intraepithelial lymphocytes increased but not to the extent seen in celiac disease.
6. Neutrophils often present (not in celiac’s disease)

Question 22

biopsy histology is generally unremarkable of this GI condition

Answer 22

1. Lactase deficiency:
   
   1. Disaccharidase Deficiency
   2. Causes profound osmotic diarrhea
2. The disaccharidases are
   
   1. located in the apical brush-border membrane of the villus absorptive epithelial cells.
   2. The defect is biochemical: biopsy is generally unremarkable.