Malabsorption syndromes

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Objectives
Define and mention the causes of malabsorption.
Discuss the local and

systemic clinical manifestations of malabsorption.
Define, explain the pathogenesis and list the clinical presentation of celiac disease.
Define, explain the pathogenesis and list the clinical presentation of whipple disease.

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Malabsorption is characterized by defective absorption of fats, fat-soluble and

other vitamins, proteins, carbohydrates, electrolytes and minerals, and water.
The most common presentation is chronic diarrhea; the hallmark of malabsorption syndromes is steatorrhea (excessive fat content of the feces).

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Malabsorption can be due to DEFECT of one or both ofthe

following serial steps :
1. Mechanical processing of food (chewing).
2. Luminal digestion (gastric, intestinal, and pancreatic juices; bile).
3. Mucosal digestion by enzymes of the brush border.
4. Absorption by the mucosal epithelium.
5. Processing in the mucosal cell.
6. Transportation into blood and lymph, through which the absorbed substances reach the liver and the systemic circulation, respectively.

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Causes :
Defective Intraluminal Digestion
Pancreatic insufficiency.
Zollinger-Ellison syndrome.
Ileal dysfunction

or resection, with decreased bile salt uptake.
Cessation of bile flow from obstruction, hepatic dysfunction.
Total or subtotal gastrectomy .

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Primary Mucosal Cell Abnormalities
Defective terminal digestion.
Disaccharidase

deficiency (lactose intolerance).
Bacterial overgrowth, with brush-border damage.
Defective transepithelial transport, Abetalipoproteinemia .

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Reduced Small Intestinal Surface Area
Gluten-sensitive enteropathy (celiac disease)

.
Short-gut syndrome, after surgical resections.
Crohn disease .

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A- Infections
Acute infectious enteritis .
Parasitic infestation.

Tropical sprue.
Whipple disease .
B- Lymphatic Obstruction
Lymphoma .
Tuberculosis.

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The passage of abnormally bulky, frothy, greasy, yellow or gray

stools.
2. Weight loss.
3. Anorexia.
4. Abdominal distention.
5. Muscle wasting
.

Clinical Features:

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Systemic manifestations:-

1. Hematopoietic system:
Anemia from iron, pyridoxine, folate,

or vitamin B12 deficiency and bleeding from vitamin K deficiency.
2.Musculoskeletal system:
Osteopenia and tetany from defective calcium, magnesium, vitamin D, and protein absorption

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3. Endocrine system:
amenorrhea, impotence, and infertility from generalized

malnutrition; and hyperparathyroidism from calcium and vitamin D deficiency.
4. Skin:
purpura and petechiae from vitamin K deficiency; edema from protein deficiency; dermatitis and hyperkeratosis from deficiencies of vitamin A.

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5.Nervous system:
peripheral neuropathy from vitamin A and B12 deficiencies.

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Celiac disease( gluten-sensitive enteropathy):
Noninfectious cause of malabsorption resulting from a

reduction in small intestinal absorptive surface area.
The basic disorder is immunological sensitivity to gluten, the component of wheat and related grains that contains the water-insoluble protein gliadin.

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Gliadin peptides are efficiently presented by antigen-presenting cells in the

lamina propria of the small intestine to CD4+ T cells, thereby driving an immune response to gluten.
Pathogenesis:-
The intestinal pathology may result from epithelial cell stress, perhaps induced by gliadin sensitivity, and CD8+ T cell-mediated killing of these epithelial cells.

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The age of presentation from infancy to mid-adulthood.
Removal of

gluten from the diet is met with dramatic improvement.
There is a low long-term risk of malignant disease. ( lymphomas, especially T-cell lymphomas).
In some patients with celiac disease there is an associated skin disorder called dermatitis herpetiformis.

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Dermatitis herpetiformis

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Tropical sprue:
Tropical sprue occurs almost exclusively in persons living in

or visiting the tropics.
No specific causal agent has been clearly identified, but the appearance of malabsorption within days or a few weeks of an acute diarrheal enteric infection.
Strongly implicates an infectious process, is that it response to broad-spectrum antibiotic therapy.

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Whipple disease:
Rare systemic infection that may involve any organ of

the body but principally affects the intestine, central nervous system, and joints.
The causal organism is a gram-positive and culture-resistant actinomycete, Tropheryma whippelii.

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Occurring in males in the fourth to fifth decades.
Cause

a malabsorption accompanied by lymphadenopathy, hyperpigmentation, polyarthritis, and central nervous system complaints.
Response well to antibiotic therapy but relapses are common.