Chapter 17 Part 5 Flashcards
What is the hallmark symptom of malabsorption?
-steatorrhea (bulky, frothy, greasy, yellow stool that has excess fat)
What are the most common malabsorptive disorders in the U.S.?
- pancreatic insufficiency (common in CF patients)
- celiac disease
- Crohn disease
Characteristics of secretory diarrhea.
- isotonic stool
- persists during fasting
Characteristics of osmotic diarrhea.
- due to excessive osmotic forces that are exerted by unabsorbed luminal solutes
- abates when fasting
The resulting loss of exocrine secretion from the pancreas in CF patients impairs which phase of digestion and nutrient absorption?
-intraluminal digestion, due to impaired fat absorption
impaired fat absorption leads to Vit A deficiency
Celiac disease is triggered by the presence of what alcohol-soluble fraction of gluten?
gliadin peptides, which may induce epithelial cells to express IL-15 that activates CD8 T-cells
What happens to gliadin peptides that cross into the lamina propria due to epithelial damage in celiac disease?
they are deamidated by tTG (tissue transglutaminase) where they interact with APC’s expressing HLA-DQ2 or HLA-DQ8 and result in stimulation of CD4 T-cells to produce cytokines that damage tissue
Where are biopsy specimens taken from to diagnose celiac disease?
-second part of the duodenum or the proximal jejunum (those portions are exposed to the highest concentration of dietary gluten)
What does celiac disease look like on histology?
- -increased number of intraepithelial CD8 T-cells
- -crypt hyperplasia
- -villous atrophy
True or False: combination of histology and serology is the most specific diagnosis for celiac disease
True; can’t be diagnosed on histology alone because intraepithelial lymphocytosis and villous atrophy are not specific for celiac disease
What serologic test is recommended for celiac disease screening?
- tTG antibody (IgA tissue transglutaminase) and EMA (IgA endomysial antibody)
- testing for gliadin antibodies has low sensitivity and specificity, so it’s no longer recommended
What are the symptoms of celiac disease in adults?
- chronic diarrhea
- bloating
- chronic fatigue
- anemia d/t chronic malabsorption of iron and vitamins
- dermatitis herpetiformis
What is the most common patient population to be diagnosed with celiac disease?
-women, ages 30-60
When does pediatric celiac disease typically begin?
-after addition of gluten into the diet between the ages of 6 to 24 months
What are the pediatric symptoms of celiac disease?
- irritability
- abdominal distention
- chronic diarrhea
- failure to thrive
- weight and muscle loss
What are symptoms of celiac disease in older children?
- abdominal pain
- N/V
- bloating
- constipation
What are extraintestinal symptoms of celiac disease?
- arthritis/joint pain
- aphthous ulcers
- IDA
- delayed puberty
- short stature
What are long-term complications of celiac disease?
- anemia
- female infertility
- osteoporosis
- cancer
True or False: HLA-DQ2 and HLA-DQ8 are helpful in confirming celiac disease
False, but the ABSENCE of them is useful due to the high negative predictive value
True or False: individuals with celiac disease have a higher rate of malignancy
True
- -enteropathy-associated T-cell lymphoma
- -small intestine adenocarcinoma
Which populations of the world are at risk of Environmental Enteropathy?
- poor sanitation and hygiene in developing countries
- -Sub-Saharan Africa, aboriginals
What are the symptoms of Environmental Enteropathy?
- malabsorption/malnutrition
- stunted growth
- defective intestinal mucosal immune fxn
What is the cause of Environmental Enteropathy?
unknown
What is the inheritance pattern of Autoimmune Enteropathy?
–X-linked
What does the acronym IPEX stand for? (IPEX is the severe familial forms of Autoimmune Enteropathy)
- -immune dysregulation
- -polyendocrinopathy
- -enteropathy
- -X-linked
What gene is affected in IPEX?
-germline “loss of function” mutation in FOXP3
transcription factor in CD4 T-reg cells
Autoantibodies to which cells are common in patients with autoimmune enteropathy?
- enterocytes
- goblet cells
- less common: parietal cells and islet cells
What is the cellular infiltrate in autoimmune enteropathy versus celiac disease?
- neutrophils in autoimmune enteropathy
- also increased intraepithelial lymphocytes, but not to the extent as in celiac disease
What type of diarrhea does a lactase deficiency cause?
osmotic
What are the characteristics of congenital lactase deficiency?
- autosomal recessive (rare)
- explosive watery, frothy diarrhea
- abdominal distention after milk ingestion
What are the characteristics of acquired lactase deficiency?
- downregulation of lactase gene expression
- can present temporarily after enteric infections
- Native American, African American, and Chinese
- abdominal fullness, diarrhea, flatulence
What are the characteristics of abetalipoproteinemia?
- autosomal recessive (rare)
- failure to thrive, diarrhea, steatorrhea in infancy
-failure to absorb fatty acids due to lack of plasma lipoproteins that contain apolipoprotein B
What is the mutated gene in abetalipoproteinemia?
-MTP (microsomal triglyceride transfer protein)
–required for transfering lipids to nascent apolipoprotein B in the ER; thus w/o MTP, lipids accumulate intracellularly
